I was called to a shop with a complaint of an ABS light on. The vehicle was a 2017 Subaru Impreza with a 2.0L engine (Figure 1). It was involved in an extensive front-end collision and experienced severe damage to the right front suspension. The shop had replaced a lot of suspension parts including a right front wheel speed sensor. They cleared all onboard control modules of error codes in memory after all the repairs were completed, but the ABS codes still remained in memory.  

Figure 1

Figure 2

When I arrived at the shop I noticed that the vehicle had multiple warning lights illuminated on the instrument dash panel (Figure 2). There was a light for the antilock brakes, stability control, collision avoidance, lane keep safe and the eye sight control systems. It is almost hard to imagine that all of these operating systems were experiencing problems at the same time. They all shared the same network so it was possible that one problem could be resonating a fault in one controller that had an adverse effect on the operation of the other controllers within the network. Many of these controllers today share input sensors among each other on a CAN bus network rather than wiring one sensor input to various controllers.  

Time to dive in 

It is always best to go into every controller and record codes stored as ”current” or ”past” codes. Then do an overview to see if these codes all point to one area of concern. If there is a problem in one controller that is on a shared network, you can almost be guaranteed that other controllers will record complaint codes redirecting your attention to the specific controller having an issue. Do not get in the habit of doing a vehicle scan of all controllers at once because you may not be guaranteed to pull ALL codes from every control module. Some scan tools may pull “present” codes but may not pull “past” codes and this could defeat the purpose of you putting together a complete game plan of attack. It is vital to compile as much information as needed to narrow down the suspect in your diagnostic routine. 

Figure 3

In this particular case, I performed a quick vehicle scan just get a basic overview of what was going on but knowing that if needed I would have to go to individual modules for a deeper dig. The engine and transmission modules on the network were pointing fingers towards the ABS control module for a fault in vehicle speed error by setting a code P0500. The ABS module stored codes C0022 for front right ABS sensor signal fault and a code C1424 for ECM abnormal (Figure 3). The right front wheel speed sensor had some kind of operational issues. At this point I had to verify the problem and decide whether it was s mechanical issue or an electrical issue. 

Most ABS systems will perform a static and dynamic test of the operating system to alert the driver of any issues. On startup there will be an integrity check just like there would be in the engine management system for component tests. This could require either one or even two-three key cycles. So I simply cleared all the codes and turned off the ignition switch for one minute. I then proceeded to start the vehicle and let it run for one minute. I did this three times to insure a three-cycle event and the warning lights did not come on at all. This is a quick procedure that can be done from the driver seat and holds great value to limit a lot of wasted time by guaranteeing that your problem is not electrical but more mechanical. Understand that the ABS module is sending reference voltage/reference ground into all of the ABS Wheel Speed sensors and checking all solenoid/relay/ lamp circuits for a driver threshold status while it validates the system during key on operation. If there were any electrical issues a light would have been on. Now it was time to go ahead with a dynamic test. 

Narrowing down the possibilities 

I went to the ABS data PIDs and selected the front and rear Wheel Speed Sensors and proceeded to drive the vehicle about 10 MPH (Figure 4). The right front wheel did not show any wheel speed signal at all and as I continued to drive the warning lights all came back on. This was definitely a mechanical condition. The culprits here on my list as I was driving back to the shop were the ABS sensor was not seated in the mounting hole properly, the tone ring was bad or the sensing device within the new sensor was bad. 

Figure 4

This vehicle uses a Magnetic Resistive type of wheel speed sensor and is not your normal AC output type. On a typical magnetic sensor, you will find a field coil wrapped around a magnet. This sensor field coil could commonly have a resistance value of about 500-1200 OHMs depending on its design and reads off a metallic trigger wheel. It will output an AC signal whose amplitude depends on the strength of the sensor magnet, resistance of the field coil and the air gap between the magnet and trigger wheel. The only downfall with these types of sensors are that they are more prone to pick up unwanted electrical noise and cannot produce enough AC voltage below 3 MPH to detect vehicle creep. 

The Magnetic Resistive type sensor looks similar to a magnetic sensor but its circuitry is different. This sensor also uses two wires, but it is dependent on a reference supply voltage and a reference ground feed to the sensing device that will in turn act on the reference voltage line to toggle it and produce a digital signal. The sensor itself will need to be triggered by magnetic bar segments and the air gap between the sensing device and magnets is crucial for proper operation. This type of sensor is more dependable because it can actually measure vehicle creep because its amplitude is not dependent on vehicle speed and it is less susceptible to electrical interference. 

The front hub bearing has a seal on each side of the bearing. Only one side of the bearing has segmented magnets imbedded into the seal along its circumference for the ABS wheel speed sensor to read. It is not uncommon for any shop to put this bearing in backwards because it can be installed in either direction. The segmented magnetic ring side must face the sensor. There is an installation tool (ATE #760130) that you can purchase off of Amazon to insure proper installation that houses a very fine metal powder in an enclosed plastic film that when placed over the proper side of the bearing will show the magnetic segments. My guess was that the bearing could be in backwards. 

I had the shop pull apart the right front suspension so I could take a close look at the repairs. This was a point where I had to perform “Sesame Street” tactics that I learned many years ago when I was but a six-year old kid watching my favorite show and singing “One of these things was not like the other.” It is so vital to perform visual inspections as part of your diagnostic routine. I had one vehicle a few months back where a shop installed a used spindle on a vehicle and the wheel speed sensor hole was offset by a half inch because it was the wrong year spindle for the car so at this point I had to keep an open mind and play outside the sand box. 

Figure 5

When I started to inspect the right-side hub bearing I could see it was installed properly with the magnetic ring facing toward the sensor (Figure 5) and everything seemed fine. At this point I was scratching my head and decided to take the other side apart to start comparing side to side measurements. As I was looking closely I sat there in awe with what I discovered. If you looked at the Wheel Speed Sensor hole on the left side of the vehicle the hub bearing was protruding three-fourths into the sensor hole diameter (Figure 6). The right-side bearing was only about one-fourth into the hole diameter. I could not believe what I was seeing and I never knew this could even happen. 

Figure 6

Figure 7

After taking out the new hub assembly and comparing it to the old hub assembly you could see that the inner part of the new hub bearing was shorter in length (Figure 7). This goes back to the old saying that the parts guy can be your best friend or your worst enemy. It’s so hard to believe that a parts guy could hand you a wrong part and at the same time an installer does not take the time to match a part up. We are in such a rush in today’s automotive world that we just don’t take the time to check everything in our routine repairs. There are no longer guarantees that you are getting a correct part or even a working part. It just ends up putting you down a different path of “denial diagnostics” that can ruin your day and create many unwanted hours of wasted time and not to mention your loss in confidence in your work. My only hopes is that this story hits home with many of you techs out there and that you keep on the watch for this not to happen to you.

Article Details

Thu, 02/01/2018 (All day)

John Anello

<p>When I arrived at the shop I noticed that the vehicle had multiple warning lights illuminated on the instrument dash panel. There was a light for the antilock brakes, stability control, collision avoidance, lane keep safe and the eye sight control systems.</p>

<p>Subaru Impreza, ABS light, service repair</p>

I’ve been working on my own vehicles since I first started turning a wrench. Not because I wanted to — it was a simple matter of economics. I couldn’t afford to pay someone else to do it for me. For the last 20-odd years, I’ve had to work in the dirt driveway of my current place of residence but was blessed a year or so ago with the chance to build a real garage next to my house, complete with two-post lift (a gift from a very good friend)!

I refer to my shop as the “Motor Age Garage” in honor of the column that has been a staple of this magazine for as long as I can remember. Writing for that column was my first role as a new contributor to the magazine, and it’s where we start our newbies to this day. By the way, we’ve got some great young talent to introduce you to!

The birth of the shop — where all the magic happens!

In addition to making life easier maintaining my own cars, it also provides me with the means to produce the videos you see on our YouTube channel and has opened up a variety of opportunities to share topics that I couldn’t before. On the other side of the coin, it opens me up to a lot of requests for help from my youngest son and his friends. I’ve done everything from oil changes to evaporator core replacements (Ford F-150, full dash removal) and soon, I’ll have his Chevy truck in for a valve “tick” that I suspect may be a wiped camshaft. Oh, the joy…

I’ll admit, there are times when I don’t feel like working on a car but I then find myself enjoying the work, getting greasy and beat up again. And I’m keenly aware that, in order for me to do my job here, I have to stay “in the trenches” as much as I can. After all, I can’t tell you guys to continue your education and skill development if I don’t!

Anyway, I recently had a project in the shop that I thought might be of interest to you. It starts with my very favorite customer – my wife.

The shuddering Scion

My better half owns a 2014 Scion tC that is her pride and joy. She’s gone full tilt with it; installing a TRD (Toyota Racing Development) exhaust, leather interior, custom lighting and more. When she cleans it up, she’ll spend a solid 3-4 hours making it look as good as it did when it first rolled off of the showroom floor. And she is just as picky when it comes to maintaining it mechanically.

My wife’s 2014 Scion tC, with a little TRD added

The car has just over 37,000 miles on it and recently displayed a new behavior that my beloved finds truly annoying. She works at the local hospital and leaves the house when it’s still dark. One recent (and also our first “cold”) morning, she headed off to work as she normally does but on the way there, experienced a severe “shudder” when she came to a full stop. The vibration was enough to cause a loud “tapping” noise that could be heard in the cabin and was strongly felt in the steering wheel. Whatever was causing the condition, it wasn’t something the ECM was concerned with – the MIL light remained off.

When she returned home later that day, I met her in the garage to see what the car was doing. Of course, I couldn’t duplicate the problem and after reviewing the scan tool data, could find no clues as to what the problem might be. So I told my spouse I would check it the next morning and she could take my vehicle to work instead.

The following day I went out to the garage and started the car up. Following the same route she takes to work, I tried to duplicate the problem but again, without success. The only difference between my drive to work and hers was the temperature. It doesn’t stay cold long in central Florida!

Waiting for the chill

A few days later, the weather forecast called for another cold night. Here was my chance! Or so I hoped.

I have an exterior/interior thermometer I use for A/C work and I first recorded the air temperature in the shop. It was reading a chilly 41°F, which matched up with the ECT (Engine Coolant Temperature) and IAT (Intake Air Temperature) readings on my scan tool. I started the car and it dutifully went into its cold start mode, keeping the idle high as the engine warmed up. I decided to monitor the ECT, IAT and engine RPM along with STFT (Short Term Fuel Trim) and LTFT (Long Term Fuel Trim) as I retraced my wife’s commute.

A few minutes into the drive, the ECT had reached normal operating temperature and the idle speed had settled down. As soon as the car came to its next full stop, I could feel the vibration and hear the tapping noise my wife was complaining of. The engine rpm appeared to be lower than it should be, hovering around 620 rpm.

It was great having a concrete floor to work on. Adding a lift, though, makes life so much easier!

Specification in Neutral is 680-780 for this car so I shifted into Park to check. Yep, that was OK and at the higher idle, the vibration and noise were gone and the engine was running smoothly. Stepping on the brake and putting the car back into Drive immediately brought the rpm down to 620, and adding the headlights dropped it even further to 580-590. That had to be too low! A quick look at the trims, though, showed perfect fuel control with both numbers staying under +/- 4%.

Next, I applied the parking brake and released the pressure on the brake pedal. The rpm increased to 670-680 and the engine condition was gone. That seemed like a more normal loaded idle speed to me and I was surprised that applying the brake pedal would result in that much of a change. After all, the transmission was already loaded. What possible difference could the brake application make? And why only under “cold” weather conditions?

I think I got it!

I admit, I was at a momentary block in my thinking. I turned to some talented techs that hang out on Facebook and got some ideas from them, and I also talked to the shop lead at my local Toyota dealer. He wasn’t too optimistic about my finding a solution, though, sharing that this was a common complaint that, to date, they have been unable to solve!

One great idea that came out of the discussions was to consider the impact the brake booster may have on the engine. The vacuum booster could be leaking and doing so only when the brake pedal was in a certain position, the shop foreman shared. He told me that he had found several similar issues when troubleshooting P0171 (System Lean) problems for his customers.

It made sense, so I thought I’d try it. I disconnected the vacuum feed to the booster and closed off the line at both ends and went back out for another test drive. And I’d like to report that the complaint had been resolved.

I’d like to, but I can’t…

The problem was still there; the vibration, the accompanying noise, and the unusual drop in rpm with the brake applied. I did identify one additional factor though. The rpm would not drop any lower than 580. I mean, I could get the rpm to drop lower by adding load but the ECM would recover and bring it back to that minimum. Yet I’m convinced that the ECM’s “minimum” was too low for the car. What else could it be?

A coked throttle body can cause idle issues, but this one was not that bad. I cleaned it anyway.

I should add, before your emails start, that I did clean the throttle body (it was a little dirty, but not badly coked) and performed an induction cleaning (setting a P0304 in the process – a possible clue?). I also performed the idle relearn procedure using the Toyota method and the aftermarket method many of my FB friends suggested. Problem is still not resolved. And, of course, I checked for any related TSBs (Technical Service Bulletins) but found nothing that helped.

But, faithful readers, I’m not done yet. My next step is to research every system that uses the brake pedal position sensor as an input. I’m also going to do some more in-depth engine inspections to see if the problem may be related to any weakness in an individual cylinder or in the VVT (Variable Valve Timing) system. I’m not ready to give up quite yet. I — and I can’t believe I’m saying this — only hope the cold weather remains around long enough for me to verify any fix I make! And I’ll be sure to let you know what I find out in a future Tech Corner column.

Article Details

Mon, 02/26/2018 (All day)

Pete Meier

<p>One recent (and also our first &ldquo;cold&rdquo;) morning, my wife headed off to work as she normally does but on the way there, experienced a severe &ldquo;shudder&rdquo; when she came to a full stop in her 2014 Scion tC.</p>

<p>Scion tC, brake booster, P0171</p>

When a vehicle shows up with a misfire, the first though that comes to mind is something ignition related like a spark plug or an ignition coil because they are such common failures. If that is not the cause, then it’s on to something in the fuel system like a clogged fuel injector or a fuel supply problem. Even though this is not the best approach, it is the one most technicians follow due to previous repairs with the usual suspects. While a good percentage of the time they are able to repair a vehicle with this course of action, when a problem occurs outside of the realm of these common items, the next diagnostic steps become unclear. Even when performing the correct steps, interpretation of the results can be misleading. This vehicle was one of those cases.

This is a 2007 Lincoln Navigator with a 5.4L V8 with 3 valves per cylinder

The patient history
The vehicle is a 2007 Lincoln Navigator with a 5.4L 3-valve Triton engine and 82,810 miles. This SUV was in approximately a week ago for a misfire concern under acceleration during the time the transmission shifts between third and fourth gear. The technician determined that the misfire was due to failing ignition coils and eight new Motorcraft coils were installed. The technician test drove the vehicle under the same conditions that revealed the problem and found that no further misfires were present. The customer was relieved to find that the vehicle did not have a transmission problem, since it was easy to see why they thought that because the misfire occurred just as the transmission was performing an upshift. The vehicle was returned to the customer and all seemed fine until eight days later. 

This is a common problem that occurs when trying to remove spark plugs on this type of engine.  While the threaded portion separates from the cylinder head, the shell of the spark plug remains seized in the combustion chamber and special tooling is required to remove it.

The vehicle returned with an almost constant misfire that was present at idle and while driving it into the shop. After a visual inspection for a coil connector that may have fallen off, the technician grabbed a scan tool and retrieved a code P0305 (Misfire Cylinder 5). He again inspected the connector by pulling it off, checking the pins on both the connector and coil and reinstalling it but to no avail. He then swapped coils between cylinder #5 and #6 and found that the misfire remained on cylinder #5. Staying with the original plan of “Misfire = Ignition Problem,” he attempted to remove the spark plug from cylinder #5. Anyone who has replaced spark plugs on one of these engines knows what I mean when I said “attempted.” The threaded portion of the spark plug and the body came out, but the rest of the metal shell remained frozen inside the combustion chamber. The spark plug was extracted without any incident and a new Motorcraft spark plug was installed. I inspected the spark plug and could not find any signs of carbon tracking or damage to the nose of the plug other than what was caused by the extraction tool during removal. 

Misfire equals something else
The misfire remained without any change in intensity and I did suggest to the technician to verify the spark plug was actually firing before reinstalling it into the cylinder head. So, if it’s not ignition, it has to be fuel right? (If Misfire ≠ Ignition, then Misfire = Fuel Problem). The fuel injectors on these engines are fairly easy to swap with only a couple of bolts holding down each side of the fuel rail, so the injectors between cylinders #5 and #6 were swapped and the fuel rail tightened back down. Of course, the engine still had the misfire when restarted, but the technician was confident that it had moved to cylinder #6. So he cleared the code and was going to test drive it to let the code prove that the misfire followed the fuel injector. Because the misfire was pretty severe, I offered to let him use my Ford IDS and its power balance test to show a graph of each cylinder and its misfire history. Much to his amazement, cylinder #5 was still the only cylinder misfiring. So he has ruled out spark and fuel, only thing left is compression, right?

An easy first test to perform with the Ford IDS scan tool is a relative compression test. While cylinder 5 is slightly lower than the other cylinders, it did not provide conclusive evidence that an internal engine problem existed.

Unfortunately, Ford does not list an actual specification for compression but rather a Min/Max range between cylinders. After the dilemma with removing the first spark plug, he was not going to remove the other seven to perform a traditional compression test. But he did test cranking compression on cylinder #5. He stated the result was 190 psi so compression was good. At this point, he threw his hands up and asked the service writer to send this one to me.

It’s got to be something!
One of the great benefits of the Ford IDS scan tool is the power balance test; but caution must be used since there has been a time or two when the wrong cylinder has been identified as the one misfiring. The misfire monitoring is a strategy that is learned, unlike a circuit code for a problem with an injector or ignition coil. There can be variances in the tooth spacing of the crankshaft reluctor, so these characteristics must be learned to enable the misfire monitor. This is usually done after the Keep Alive Memory (KAM) has been cleared and is accomplished by performing a few decelerations from 60 mph to 40 mph without braking. The fuel is cut to the engine so no combustion takes place during the learning process eliminating that variable from the calculation. There should also be a code P0315 (Unable to Learn Profile) if the vehicle was not able to learn the profile correction. That code was not present, but that does not guarantee that cylinder #5 was the one misfiring.

I have chased an incorrectly identified misfiring cylinder before, and it was a frustrating learning experience. A simple way to verify that the correct cylinder is being identified is to create another misfire or two on different cylinders from the one identified and verify that those cylinders are correctly identified also. I perform this by watching the power balance test and unplugging a coil on a different number cylinder and verifying it is correctly shown on the test. An injector would have the same effect if it is easier to access than the ignition coil. Needless to say, cylinder #5 was the one with the misfire so that eliminated that possibility.

Another test that should be performed on any vehicle with a misfire before delving too deep is a relative compression test. While I usually perform this test with an oscilloscope, a current clamp, and sync it with the cylinder #1 ignition coil, the Ford IDS has a built in test that can be performed by depressing the throttle fully to the floor (to prevent fueling during the test) and cranking the engine for 10 seconds.

What I did find when performing this test initially was that cylinder #5 had 4 percent lower compression than the other cylinders, indicating the possibility of a mechanical engine problem, but it seemed too small of a difference for this scenario. However, since the cylinder was misfiring, not to mention a fuel injector swap between cylinders, there was also the possibility of a cylinder wall that has partially washed down from excessive fueling.

While the other technician already swapped the ignition coil and fuel injector from cylinder 5 without any change in the misfire for that cylinder, I needed to verify that the actual signals which activated the ignition coil and fuel injector were present, since even a known good component will not work correctly without the proper signals.

Even though the previous technician swapped the ignition coil and fuel injector from cylinder #6, that didn’t mean that there wasn’t an issue with the signals from the Powertrain Control Module (PCM) or wiring to the fuel injector or ignition coil for that cylinder. I attached a scope to both the fuel injector and ignition coil of cylinder #5 and found that both were receiving the correct voltage signal and were operating as designed. At this point I am satisfied that there is some type of mechanical problem affecting only cylinder #5. 

Cranking compression isn’t the whole story
An easy test to perform without removing anything other than the vacuum hose is to perform a cranking vacuum test with a First Look Sensor (FLS). I installed the FLS into the hose going to the vacuum brake booster and synced to the Cylinder 1 ignition coil. The FLS measures changes in pressure, so this means that each time an intake valve opens a downward hump or “pull” is indicated in the waveform.

Here is the capture using the First Look Sensor in the intake while synced to the cylinder #1 ignition coil. Note that the intake pull for cylinder #1 starts approximately 360 degrees from when the ignition coil fires.

An engine in good condition will produce a consistent and relatively even pull for each cylinder in the firing order, since each cylinder should be drawing the same amount of air and each intake valve should be open for the same amount of time, but when an engine has a problem the steady repeatable pattern will become erratic. This is where the sync comes in. By triggering off a known good cylinder and using the rotational rulers of the scope, it is possible to divide the period between ignition firings into eight evenly spaced divisions with each representing an individual cylinder. Keep in mind that the intake stroke for the cylinder that has the ignition sync occurs about 360° before the intake stroke. The firing order for this engine is 1-3-7-2-6-5-4-8. Looking at the capture, there is definitely a problem, but it is not something that most can pick out unless they are very familiar with FLS pattern recognition.

Here is the same capture with the relative piston stroke position of cylinder 5. Notice how the symptom of a leaking intake valve does not show up during the intake pull of cylinder 5 but the effect it has on the other cylinder’s intake pulls depending on where the cylinder 5 piston stroke position is during their intake valve opening.

The pull for cylinder #5 looks fine, however where the intake pulls for cylinders #3 and #7 should be, there are actually pushes or upward pulses. One of the reasons behind this type of a pattern is that if the intake side of cylinder #5 is not sealing, it can leak cylinder pressure back into the intake manifold (where the FLS is connected to) and disrupt the normal balance between cylinders. However, I am not confident enough in my abilities to make the call just yet so a little more testing needs to be performed first.

The cranking compression results found while using the Pico WPS-500X pressure transducer matched what the previous technician found using a mechanical gauge.

While there are no definite specifications listed for compression of this vehicle, 190psi would normally be a very good number on most vehicles.  However after a few more revolutions, the number started dropping.

Since the other technician had already broken the original spark plug while trying to remove it and installed a replacement, I was not hesitant to remove the new plug and install a compression hose attached to a pressure transducer for my next test. If that was not the case on this type of engine, I would have opted for different testing methods rather than risking removing and possibly breaking the spark plug unless absolutely necessary. With the pressure transducer installed and the injectors disabled, a cranking compression test is performed, and I was a bit confused by the results. I know the previous technician also performed a test with a mechanical gauge, and I also came up with the same results – 190 psi of cranking compression and did not notice any discernable indications of a mechanical failure.

However, is 190 psi of compression good? Is it high? Is it low? Remember, Ford does not list a min/max specification, only a range between what the highest and lowest cylinders can vary by. Based on what happened with the first plug that was removed, I am definitely not going to remove more spark plugs to perform comparison compression tests. Something interesting to point out is that as the cranking compression test continued, a decrease in pressure occurred by almost 14 psi as shown in the capture. The next test to perform, especially since the pressure transducer and compression hose are already installed, is a running compression test. 

The running compression test is where the problem is revealed.  Normallthe compression would be between 1/3 and 1/2 of the cranking compression reading, but here it does not even reach 16psi.

A look inside
For the previous technician and several others, this is an overlooked test that reveals a lot of information. This is a dynamic test compared to the cranking compression test and some performance and tuning shops use this test to determine how well a particular cylinder is contributing to the engine. The test is performed with the fuel disabled to the cylinder being tested, which on this vehicle was as simple as unplugging the injector and running the engine at idle. The pressure of a good cylinder should be approximately one-third to one-half of the cranking compression test result. A throttle snap is also recommended during a running compression test, which should be approximately 80 percent of cranking compression results for that cylinder; however, when using an in-cylinder pressure transducer instead of a conventional compression gauge, it is not uncommon to see a higher reading than on the original cranking compression test. So, starting the engine and reading the test results showed a startling discovery — the running compression for cylinder #5 was only around 16 psi, a lot less than the 63-95 psi that would be expected and a snap throttle only increased to 70 psi.

While the vacuum achieved on the expansion stroke appears good at 21inHg, the vacuum reached during the intake stroke is around 15inHg, indicating an intake valve is not sealing.

On a healthy cylinder, this would have been 150 psi or higher, but was under half of that number. A good amount of the time, when snap throttle results are lower than expected but the running compression is normal, the problem lies in the intake side of the system, and if they are higher it points to the exhaust side, sometimes a restriction. This, however, showed very low running and snap throttle results. So now we know we definitely have an internal engine mechanical problem on cylinder #5 which is going to be intake related. This is also gathered from looking at the vacuum achieved on the expansion stroke and intake stroke. Usually both vacuum pockets are in the vicinity of a normal engine vacuum and are even with each other. When the expansion stroke vacuum is relatively good and the intake stroke vacuum is low, it generally points to an intake valve not sealing. The reason the expansion stroke vacuum is relatively good is because when the intake valve is leaking, it is open to the intake manifold where a vacuum already exists. An important point to remember that I was taught in pressure transducer training class is that the camshaft lobe opens the valve, but the valve spring closes the valve and keeps it closed.

With the driver side valve cover removed, a broken spring for one of the two intake valves of cylinder 5 is found.

Going by these observations, a phone call was made to the customer and approval was given to remove the Bank #2 valve cover for further inspection. With the valve cover on the driver side removed the test results were confirmed. One of the two intake valve springs for cylinder #5 was broken which was the cause of the misfire. 

An old-school style technique was used to hold the valve in place while changing the spring. Some small nylon rope was fed into the spark plug hole while the piston was at the bottom of the cylinder and then the crankshaft was rotated to compress the rope against the face of the valve which worked perfectly. The rocker arm pops out and back in without any bolts but a specific type of valve spring compressor was needed due to space constraints.

The cause of the misfire, a broken intake valve spring on cylinder 5.

Once everything was reassembled the Navigator idled and drove smoothly without any further misfire complaints. With ignition being such a common cause of misfires it can sometimes be hard to step back and consider basic mechanical failures, especially with modern engine reliability. However, with the increased amount of labor required to remove engine covers and components for inspection, old style tests can be performed with new tools and techniques to help isolate problems before teardown.

Article Details

Thu, 03/01/2018 (All day)

Michael Miller

<p>This &rsquo;07 Navigator had a misfire. Follow along and see if you would have taken these same diagnostic steps.</p>

<p>Lincoln Navigator, misfire, diagnostics</p>

I started out my diagnosis on a 2003 Ford Escape with an automatic 3.0 VIN 1 24 Valve V-6 just like I would any other vehicle that I bring in the bay. First, the customer interview to gather the information and the complaint — with just shy of 200K on the odometer, the MIL light is on — then gather some codes and data, come up with a plan, repair and verify and then move onto the next one. Little did I know my plans were about to be derailed! 

Figure 1

Figure 2

The customer had no complaints other than a glowing MIL light. A quick scan revealed a P0452 "EVAP System Pressure Low" both pending and current (Figure 1). Nothing new for us in the rust belt to see EVAP codes on a day to day basis, that's for sure! While sitting in the driver's seat, I decided to have a quick look at the Fuel Tank Pressure (FTP) data PID and quickly discovered it was at 2.6v KOER, which is normal for a Ford EVAP pressure sensor sitting at atmospheric pressure. Wanting to see if the FTP sensor would respond to vacuum, I opened the vapor management valve (purge solenoid) with the scan tool and saw the voltage drop to around 2.19v (Figure 2). That is about what I would expect to see considering the canister vent was still open. OK, so what is going on here? I don't recall at the time what possessed me to increase the rpms, but I did. Perhaps it was in an effort to gain a bit more vacuum on the decel while watching the FTP data PID with the vapor management valve still open. Whatever the thought was, it turned out well because it revealed the problem! At EXACTLY 3000 rpms, the FTP data PID would drop straight to zero volts (Figure 3)! OK, you have my attention, I thought.

Figure 3

Figure 4

I now knew what the ECM was looking at and why it flagged the code. After all, it met the code setting criteria. It was time to get to know my enemy. I pulled up a wiring diagram to see what I could gather from it and verify what I already knew (Figure 4). It is a standard three-wire 5v pressure transducer that was easily accessible under the driver side rear seat. A ground wire, signal wire and a 5v reference. It also shared the same 5v reference as the Differential Pressure Feedback EGR (DPFE) and the Throttle Position Sensor (TPS). Thinking to myself that if the sensor shares the 5v reference and it was losing it, and it happened to be at or before that splice S105 that I saw in the diagram, certainly we could see that in scan data because it should affect the other sensors sharing the same 5v reference, right? 

Time to test a theory

After a moment of recreating the conditions and monitoring the TPS and DPFE PIDs, they appeared to be unaffected. I knew it could not be losing the ground side because if that were the case, the voltage should go high. I verified this by simply unplugging the sensor and indeed it did go high (Figure 5). While I still had the sensor unplugged, I recreated the conditions of the fault and the signal stayed nice and steady. However, after plugging it back in the condition was still present (Figure 6). That being said, we did not correct the condition by unplugging it or messing with the harness. You know as well as I do how frustrating that can be.

Figure 5

Figure 6

Now that I had grabbed what data I could, I decided to grab a graphing DVOM and have a look at the wires right at the FTP sensor in hopes to get an idea as to what was going on. It is a two-channel meter, so I monitored the 5v ref, signal wire and ground all at the same time and it revealed exactly what the scan tool was showing. When the signal wire dropped to 0v at 3000 rpm, the ground and 5v ref stayed perfect. Or so they seemed. Not really knowing where to go next, I decided to just double check the circuit integrity of the signal wire from the ECM to the FTP sensor. I unplugged the FTP sensor and the ECM, supplied battery voltage on the signal wire and with a 780mA test light on the other end and it seems to carry current just fine (Figure 7).

Figure 7

Figure 8

At this point, I really just don't know. With a shop parking lot full of other work, it was getting hard to concentrate. It is a terrible feeling as a mechanic and shop owner, as many of us know. Part of me is thinking the ECM is gone wonky but the fact that it is so predictable and it only does it at 3000 rpm is still weighing in my mind. I decided to play some "swaptronics" and substitute a known good (used) FTP sensor (Figure 8). A quick trip to see my friends at the local salvage yard and we were back at the shop. Used sensor is now installed and low and behold it does the same exact thing! Needing to think for a bit I decided to gather a bit more data on a test drive and it revealed that driving it made no difference and it still drops out at 3000 rpm. Engine torque, bumps, forward, reverse, hot or cold, nothing made a difference.

Not beaten yet!

Feeling like I am at the end of my rope and out of ideas for the moment, I decided to use my "phone a friend” life line. I called my good friend and mobile tech Keith DeFazio from New Level Auto Diagnostics in Staten Island, NY. We discussed what tests had been performed and what the possible causes were, and tried several things such as unplugging DPFE, TPS and retesting. 

Low and behold, unplugging either the DPFE or the TPS sensors caused the problem to disappear! WHY!? Was something happening on the 5v reference? It was time to have a closer look, using the scope feature on my DVOM. With the scope hooked back up, there it was — staring me in the face. At 3000 rpm, the 5v reference would go into a high frequency hysteria, for lack of a better term (Figure 9). Seeing this only brought about more questions though. The main one being, where is all this noise coming from and why is it effecting the signal wire and making it drop right to zero volts? 

Figure 9

While I was still contemplating ideas in my head knowing I was one step closer, I needed to know if the signal was being "sent" by the ECM or "received." The easiest way to do that was to just cut the wire near the ECM and scope both ends of it and I discovered it was coming from the FTP sensor to the ECM. I still had no idea why though. However, it did lead me away from thinking it was the ECM at the time. All I knew was something was changing at 3000 rpms and was effecting it. Of course, at this point I have tried unplugging the coils, the alternator and various other components, just to try and get an idea where this noise is coming from and was not making any progress. I decided to study scan data some more to try to gather some clues as to what could be changing. I thought to myself, is the alternator duty cycle changing, is there a device or output turning on at the same time, ANYTHING! Still nothing. 

Deciding to call it a night after a busy day at the shop and working on this in between other cars, I figured it is best to go home and sleep on it hoping it comes to me in a dream. Laugh if you want, but I am certain many of you have been there before! I woke up in a panic at 3 a.m. and rushed back down to the shop to fix this mind-bender. On my way out the door, it dawned on me I never saw a Power Steering Pressure (PSP) switch input on the scan tool. Could that be changing? I clearly remember thinking to myself, "that is a 5v switch, right?" I walked back in the shop, fired the scan tool back up and unplugged the PSP switch. I GOT IT!!! The problem was gone! But why!? 

At this point, part of me did not care, but the rest of me wanted to know what was going on. I grabbed the scope, back probed the connector and there it was (Figure 10). The PSP switch at 3000 rpm was opening and closing like a mad man. I also discovered I was wrong; it is not a 5v switch — it is indeed a 12v switch. Good thing I was tired and did not give it a second thought. Had I known it ran off a 12 circuit would I have gone back in and checked it? Hard to say at this point. As they say, hind sight is always 20/20.

Figure 10

A new PSP switch was fitted the following morning. The EVAP code was repaired, drive cycle was completed and the symptoms were corrected. As a mechanic who grew up in this field and learns from self-study and by getting my butt kicked from time to time, this one humbled me and taught me a few things. The first thing it taught me was to use my scope feature from the get go even if it seems unnecessary. You never know what it might show you. It also reminds us sometimes we do need to walk away, clear our heads and not give up! I also learned the value of having a great friend in the industry who shares the same passion for repairing vehicles as I have and is always willing to bounce ideas around.

I tend to chuckle every time I have a vehicle come in now with an EVAP code tripping the MIL because you just never know. It may just need a new power steering pressure switch! Who would have thought.

Article Details

Sun, 04/01/2018 (All day)

Eric Obrochta

<p>I started out my diagnosis on a 2003 Ford Escape with an automatic 3.0 VIN 1 24 Valve V-6 with the customer interview to gather the information and the complaint &mdash; with just shy of 200K on the odometer, the MIL light is on. Then I gather some codes and data, come up with a plan, repair and verify. Little did I know my plans were about to be derailed!</p>

<p>EVAP Code P0452, auto repair, South Main Auto</p>

We begin the saga at Assured Autoworks in Melbourne, Fla. This reputable shop is owned and run by my good buddy, Brin Kline. Like many times before, he acquired the subject of this month's article as a “tow-in” from another local shop. The original complaint from the owner of this 2011 Chevrolet Aveo — with a 1.6L MFI with an automatic transmission and 59,661 miles on the odometer — was that the vehicle lacked power output and had DTCs pertaining to an exhaust cam sensor fault. Upon further investigation, the original repair shop found a broken reluctor tooth on the exhaust cam. The cam was replaced, along with the timing chain, guides and both the intake and exhaust cam phasers. That repair, although obviously required, led to disappointment and self-doubt as the MIL remained illuminated and the vehicle still performed unsatisfactorily. The original repair shop disassembled the front of the engine many times to double and even triple-check the cam timing only to find everything still appeared to be indexed as intended. The original shop also pointed out several clues that led them to believe the cylinder head had been replaced with a used one. That included the heat-sensitive "button" designed to indicate if the engine was ever overheated. It was noted that the vehicle was purchased wholesale and that no further history of the vehicle was known. This is where Brin jumped in to apply his skillset as a diagnostician, a skillset his shop has developed a reputation for. 

Grabbing the low-hanging fruit 
The vehicle was scanned for DTCs (Figure 1). Brin and his tech quickly ruled out the cause of the first two DTCs as both solenoids were left disconnected from the previous shop’s diagnostic attempts. All DTCs were cleared and a road test of the vehicle was carried out…at least, the attempt was made.  At an idle of 735 rpm, the little Aveo’s 1.6L engine generated a manifold vacuum just slightly stronger than 11 in/Hg (Figure 2).

Figure 1

Figure 2

From experience, we expect vacuum levels closer to 20 in/Hg (at sea level) from a healthy engine.  Sometimes the engine struggled to idle and other times, it simply couldn’t get out of its own way. During the road test, the faults for MAF and MAP were obvious. As stated above, the vehicle had performed very poorly, almost as if the cam timing was set incorrectly or it was starving for fuel. Brin monitored some key inputs regarding the breathability of the engine, considering the exhibited symptoms, to help pinpoint the nature of the fault. These PIDs will determine if the engine is being fueled properly or not and if the incoming air is being weighed properly. They included: 

• ACTUAL and DESIRED camshaft positions 
• MAF 
• MAP 
• ACTUAL and DESIRED throttle angle 
• LOAD 
• Fuel Trim 

The vehicle again failed to accelerate properly. Although it lacked power, the throttle position indicated the PCM’s intent to accelerate. The car, however, did so reluctantly. The throttle position displayed approximately 48 percent when the APP indicated a request for acceleration (perhaps a state of “limp” or “default?”). This made it impossible to perform a proper Volumetric Efficiency test. The fuel trim showed no signs of correction indicating that the engine was fueled properly, given the amount of air it was inhaling.  What’s contradictory, though, is the camshafts’ DESIRED and ACTUAL PIDs reflect no deviation from one another. Meaning, the timing components were installed correctly and phasing as commanded (Figure 3). 

Figure 3

Justified exploratory surgery 
Reviewing the scan data, the PCM seems happy. It’s breathing right… but it’s not breathing right, if that makes any sense. Proving what is good with the engine holds as much diagnostic value as discovering what is wrong with it. One way to verify that the PCM is correct in its interpretation of camshaft/crankshaft correlation is to scope the signals over an entire engine cycle. Brin did just that with his scope. He then used the scope’s vertical cursors to determine how many degrees each camshaft signal transition was from a common point of reference. Like many elite technicians, Brin is one for sharing information to better hone his skills and so that others may learn as well. In return, when Brin calls on his pals for some needed info, they are happy to oblige. Reaching out to friends across the country, Brin had access to the same capture but from a known-good vehicle. He simply compared his capture to the known-good and determined that (according to the camshaft/crankshaft signals) the engine was timed properly (compare Figure 4 and Figure 5).

Figure 4

Figure 5

Of course, the possibility of a damaged locator or shear key could certainly have one of the shafts out of time, while the reluctors remained in time. He could certainly have removed the valve cover for a visual inspection to prove or disprove that theory. However, Brin values his time and through networking with other like-minded technicians, Brin has learned and practiced (many times over) using his mind and tools to force the fault to surface, rather than chasing down the fault. In lieu of disassembling the top of the engine for visual inspection, a more efficient approach was chosen initially. Using a series of easy-to-perform test procedures to justify more involved forms of analysis likely leads to the most efficient diagnosis. With the use of an in-cylinder pressure transducer and the scope, Brin observed the changes in pressure for one of the cylinders while cranking the engine over through multiple engine cycles. This allows for an evaluation that will yield him a reason for disassembly. Like many others, Brin doesn’t wish to disassemble anything unless he knows he will find a fault. That is exactly what this type of testing will provide for him — a reason to disassemble. 

Multiple arrows in the target 
Like any other type of testing, practice and acquiring a library of known-good captures will give you the trained eye required to spot bad because you’ve become confident in what good looks like. While viewing the in-cylinder compression capture acquired from our poorly performing Aveo, the waveform exhibits some very strange characteristics.  When compared to the known-good captures Brin has access to, the peak compression is significantly lower in the suspect vehicle. What’s very strange is the fact that a visible exhaust plateau is present during cranking. This is a very atypical characteristic of a cranking compression event. The presence of this plateau is due to the in-cylinder vacuum of over 16 in/Hg being generated (Figure 6).

Figure 6

What’s equally as revealing is the late closing of the intake valve. The late intake cam is the most likely cause for the deep in-cylinder vacuum as well as the low compression (see Figures 7 and 8). 

Figure 7

Figure 8

So, lets recap for a moment: 

• no timing correlation DTCs, but breathability DTCs present 
• engine breathes improperly and performs poorly 
• fuel trim doesn’t indicate a skewed air mass input 
• timing signals indicate proper cam/crank correlation 
• in-cylinder pressure testing exhibits a very late intake camshaft 

There is no doubt that a mechanical fault is present in the engine. How can this be? Perhaps a damaged keyway on the intake camshaft?  

The fireside chat 
A discussion was carried out via FaceBook Messenger among a group of enthusiastic diagnosticians. We analyzed the information that Brin presented to us and weighed the facts. Due to the indication of the used cylinder head installation, we used logic and determined that perhaps an incorrect intake camshaft was installed (difference in application). With this information, the confidence grew and Brin found a known-good in-cylinder capture from a previous model year of the same vehicle platform. Again, the networking provided him with the capture. It reflected, almost identically, the same characteristics of his suspect vehicle. A new intake camshaft was ordered and as you can see by the comparison of the intake camshafts, the proof is clear (Figure 9).

Figure 9

The reluctors are configured the same. It’s the actual clocking of the lobes that is significantly different, model year to model year. It conclusively explains: 

• why no correlation DTCs were present 
• why the cam/crank correlation waveforms reflected proper timing 
• why the engine performed so poorly 

Fishing with a net instead of a pole 
Regardless of your level of experience in any realm, including automotive drivability analysis, there is always someone who has some experience, information or data that you don’t currently possess. Said another way, it's beneficial to network with others. With the compound knowledge and experience, everyone involved prospers and grows. The automotive industry as a whole continues to move forward in a positive direction and you will build friendships that can last a lifetime. 

I want to take a moment to not only thank all of the participants who took the time to offer their input but also indicate where the participants of this case study were actually located. It still amazes me that we can be thousands of miles apart and still have a conversation like we are all elbows up at the bar, enjoying a few beers together! 

Special thanks to these gentlemen for their contribution: Brin Kline, Assured AutoWorks in Melbourne, Fla.; Brian Culotta, Dave's Auto Care in Chardon, Ohio; Justin Miller, JM Diagnostics in Herriman, Utah; Matt Wallce in Clover, SC; and Scott Brown, Diag.net in Fontana, Calif. 

Article Details

Tue, 05/01/2018 (All day)

Brandon Steckler

<p>We begin the saga&nbsp;at&nbsp;Assured&nbsp;Autoworks&nbsp;in Melbourne, Fla. This reputable shop is owned and run by my good buddy,&nbsp;Brin&nbsp;Kline.&nbsp;Like many times before, he acquired the&nbsp;subject of this month&#39;s article&nbsp;as a &ldquo;tow-in&rdquo; from another local shop.</p>

<p>2011 Chevrolet&nbsp;Aveo, DTC, auto repair</p>

One particularly cold day, I was on my way home from work and I saw a couple of women standing by a black Cadillac crossover that was parked in the grass beside the road. I pulled over to see if I could lend a hand. I was in my uniform, and I assessed their situation — quite simply — they had a flat tire on the right front. I opened the hatch on my Explorer, got out the small jack and four-way lug wrench I carry, and went to work changing the tire. I do this kind of thing regularly when I see people beside the road with flats, because almost nobody knows how to change a tire any more, and rural Alabama isn’t as dangerous as a big city. I was about half done when a wrecker arrived, and the wrecker driver watched me finish changing the tire and said something about the donut and how it should be installed on the back. I pointed out that this donut was the same diameter as the regular tire, so the gears in the differential wouldn’t suffer. I heard the driver tell the women he was on the other side of town when he received the call and wished he had been able to get there sooner.

It was about that time that I realized I had accidentally bumped the wrecker guy out of a roadside assistance call. I would never have changed the flat had I known he was on the way, but they didn’t say a word about having called anybody. It was then evident that they thought I was their roadside guy because of my uniform – and the wrecker guy showed up in jeans and a bomber jacket. As I was putting my tools away, one of the very confused women asked in her crisp British accent if they needed to sign any paperwork.

“Nah,” I told her as I closed my hatch. “I’m just on my way home from work.” 

The 2004 Trailblazer

When we got the pan off the Trailblazer, we saw this dreadful mess. Running an engine short distances, too cool, or without necessary oil changes comes with a price

A customer came walking into my office asking if we could put an oil pump on the engine in his Trailblazer. He was an older fellow who had convinced himself that a new engine heart would silence his suddenly noisy powerplant. Out of respect and diplomacy, I spent more time discussing his request than was necessary. Semi-knowledgeable customers like this usually need their thinking gently redirected, and I convinced this fellow that, before we spent the time and effort fiddling with the timing chains and everything we’d have to hurdle on the way to installing the oil pump he had already bought, we needed to do some exploratory surgery, and after a short dialogue, he saw my point.

I wrote a work order, and we removed the oil pan to find large slivers of at least one rod bearing swimming in the pan-sludge – some of which was still clogging the screen. We pulled the rod caps one at a time until we found that #2 had burned out and shed the metal that had wound up in the oil pan. He’d need an engine, and that was that.

This was the only rod that burned out on the Trailblazer – interestingly, the rest of them looked good.

This reminds me of another fellow a few years back who was doing some contract work with a group of builders on a local campus. He came to me one morning and told me his Ford Ranger 4 cylinder had begun to rattle a bit, and that the oil light had come on just that morning. I told him his oil screen was likely clogged with sludge. In the parking lot, that character drained the crankcase oil into a large-mouthed jug and used a little flashlight to examine the oil pump screen through that tiny hole, and sure enough, it was clogged. He got some kind of aerosol spray from the parts store, along with oil and a filter, and working through the oil drain plug hole, he cleaned the clogged screen and then did what he could to flush that stuff out of the oil pan – all by just removing the drain plug. And he fixed his Ranger — at least, temporarily.

The 99 Mazda 3.0L, a Caravan and a Freestar

Nick is one of my guys, and he told me his truck was losing water and running hot — it had a leaking hose, but he had added water and had driven it until he had damaged it to the point that the compression was pushing its way into the coolant. Blown gaskets prevailed, and it was his only ride, so we got started yanking the heads off. If he was fortunate, head gaskets would be all he’d need, but he wasn’t fortunate — as it was, he needed a cylinder head, and that ran the bill up a bit. He finished the truck, paid the bill, and got his ride back.

The 99 Mazda got hot enough to crack this head, and a new one was in order. A few hundred dollars later, the B3000 was back on the road, at least until its next breakdown.

After misfiring on a parasitic drain diagnosis the first time and replacing the BCM with a used one (which changed the odometer reading; we had to straighten that out) we finally caught the Caravan’s intermittent in the act and pinpointed the FCM in this TIPM as the problem. It was keeping the accessories fired up even after the door was opened..

The college owns a 2005 Dodge Caravan with nearly 200K on the clock, and that vehicle’s status changed from being driven every day to being driven about once a week, and a parasitic drain suddenly raised its ugly head. About half the time whenever a driver would obtain the keys to use that vehicle, the battery would be dead. With the PICO connected via an inductive clamp, we discovered a significant drain that evaporated when the accessory relay was removed, and when we’d remove that relay, we’d feel the “click” of the relay coil releasing — that relay was remaining energized constantly after it should have gone dark, and that was keeping the radio, power windows, etc. up and running even after the driver had exited the vehicle. It wouldn’t do this every time, but we caught it doing this during our diagnostics. On this vehicle, the front control module energizes the accessory relay, and that module is part of the TIPM — the smart fuse box, if you will. With the scan tool connected and the problem present, we saw no reason why the accessory relay should have been remaining energized, and we were lucky enough to find the right replacement TIPM for $100 at a local salvage yard. Game, set and match on that one.

The 2005 Freestar wasn’t overheating, but it was an occasional no-crank. We found that we could bypass the secondary terminals in the relay socket and the starter would spin, but that there was no juice at all making it from the ignition switch to the starter relay coil. The theft light wasn’t blinking and there were no related codes, so we checked connections between the ignition switch and the starter relay and found a time-corroded set of chalky terminals at TR sensor pin 12 that turned out to be interrupting the current to the relay coil. Had this been a high-current circuit, this oxidized terminal would have melted the connector. That one was an easy fix.

The Freestar’s TR sensor had a time-oxidized pin 12 – that was the reason for the stubbornly intermittent no-crank. There are pigtails and terminals to be had – at a cost. But that’s the best fix for a problem like this.

The 2004 Land Rover

A guy came to us with a 2004 Land Rover that was leaking brake fluid and had a no-blow problem with the A/C — the blower was dead, and one of my guys did some Googling, as young guys with smartphones are wont to do — it seems that half the people who owned a Rover of this generation had a dead blower motor and nobody seemed to know the root of the concern, but everybody was running overlays. With a desire to know why, we dug up the schematic. In the panel, the fuse was good, and power was passing through it, but when we finally found the blower relay (which was annoyingly difficult, but Identifix® has the information, albeit for an RHD vehicle), we discovered that there was no power at the relay common terminal — it had nothing to deliver to the blower motor.

This guy bought a Land Rover for a hunting truck. Not sure why he went so far out of his way to locate one of these, but he did. There aren’t many of these around here either.

Backtracking to the fuse panel connectors, we found the wire that was supposed to be feeding the relay and it was dark — it turned out that the innards of that fuse panel had gone open, and now failed to deliver voltage to the motor — the fuse panel was the weak link in the chain, and it had fallen prey to time, chance and obsolescence. But rather than launching a nationwide search for a salvage yard replacement fuse panel for a 2004 Land Rover, and rather than having the guy get a title loan just to buy a new fuse panel, we opted for the workable fix that would strengthen the chain rather than simply replacing the weak link. An overlay isn’t a bad fix in cases like this.

When we backtracked from the relay to the fuse panel output terminal on this circuit, we found that the fuse panel wasn’t feeding the relay – and so we ran the overlay.

This blower situation isn’t that uncommon and never has been, because blowers pull a heavy load. Back when Ford vans still had glass fuses in the panel under the dash, they would develop a similar problem — they wouldn’t necessarily blow the fuse, but the fan would fail because the solder would melt out of the end of that glass fuse due to heat and resistance within the panel, and Ford had us cut the wires at the panel and install a 30-amp breaker.

In the Land Rover’s case, we got an inline blade fuse holder and a 30-amp fuse, and beginning at the battery junction under the hood, we fed a 12-gauge wire through a loom back through the bulkhead grommet to the relay common terminal, and the blower was resurrected with a solid, lasting repair. I showed the owner where the new blower fuse was and how we had run the overlay through loom along the harness, and he was a happy camper.

The Land Rover’s master cylinder was leaking at the reservoir grommets and we replaced the master cylinder, reservoir and all, to stop the fluid leak — that was a straightforward fix.

A problem two years in the making

The title vehicle for this article is a 2008 Chevy Impala with a 3.9L V6 and 124,654 miles on the odometer that came in on the hook with the report that it was making a horrible racket and couldn’t be driven. What we found was that the #1 spark plug had blown out of its hole. That’s the one under the alternator. Now, this is one of our company cars, and while I didn’t dig into my records when the vehicle first came in, I didn’t remember us ever replacing the spark plugs on this one — not in recent history anyway. It was also sporting a set of replacement wires, which I didn’t remember us replacing.

The 2008 Impala

The problem was that when we tried to install another spark plug in that hole, we found that the plug would tighten down to a certain point and then pop loose again — over and over. Using the Autel inspection scope’s magnified image, we saw threads that didn’t really look that damaged, but the fact remained that a spark plug wouldn’t screw into that hole and tighten up. Looking more closely at the actual spark plug that had blown out of the hole, it appeared that there was some kind of gray material in the threads. What I later realized was that the gray stuff in those threads was probably due to the fact that the spark plug had originally been screwed all the way in, but it hadn’t been properly torqued, and that it had spent a long time bouncing in the threads and slowly screwing itself out of that hole until it was dislodged by compression and combustion.

My initial take on this situation was that no matter how, where or why this happened, we needed to come up with a fix. The alternator had to be removed, and we had to decide what we were going to do about that situation. Another close-up scope shot revealed threads that looked fairly normal, and the threads on the spark plug didn’t look stripped, but I opted (right or wrong) to put a thread insert in that hole for good measure. Of course, when tapping threads in a spark plug hole, it’s wise to first force air into the throttle body and turn the engine over until positive pressure is blowing out the spark plug hole, and that’s what we did. An entire new set of plugs was installed and torqued, and at the time of this writing, the car is still on the road.

But when I researched the work we had done on that company car over the years, I found that somebody under my supervision had replaced the spark plugs some two years ago — almost to the day — but I couldn’t find a record of who did the work, only that we had purchased spark plugs and wires for that vehicle back then. The fact that the errant spark plug stayed in place for two full years before leaving its hole was amazing — that car has gone tens of thousands of miles with multiple drivers. And there was no evidence that the spark plug had overheated, either. Time and chance had struck again.

Rust-ravaged by time

Speaking of Impalas, a 2006 model came to us needing brake work (scrubbing in the rear), and this one had spent its prime years in New York. With that in mind, the readers who live in those northern road-salt climates know what time and chance does to cars up there. One of my students made the remark that cars in the South rust from the top down and cars in the north rust from the bottom up. Down on the Texas coast, some of the shops used to regularly spray the underside of cars with oil to protect them from the salt air. I’m not sure if anybody does that anymore.

The left rear inner brake pad was long gone on this Impala and the caliper piston was kissing the rotor with every brake application. If that wasn’t enough, the car was blessed with enough rust — particularly on fluid-carrying lines — to make it very dangerous to drive. The fuel return line had even rusted through back near the gas tank and was leaking, and the brake lines were one heavy application away from a sudden death situation. It would have been a matter of time before the brakes failed, and it was only by chance that this vehicle wound up on our lift before it happened.

You can see that this caliper piston had worn the pad and its metal backing to powder – and all that was left was this silencer shim. It got this caliper replaced, all the rear brakes, 2 rotors, and…	… before we were done, it got a replacement fuel line and some new brake lines – this was a New York nightmare. The wet area is from the rusty fuel line gas leak.

The brakes got replacement rear rotors, a new left rear caliper, and brake lines to the rear, which we built with bulk tubing, complete with ISO and double flares as required. The leaking fuel line was replaced from stem to stern with a new steel line, but I had to cut an 8mm return line pipe off an old fuel pump and compression-union it to the replacement fuel line so the plastic quick-connect would work back at the tank. Oh, and we also replaced the rusty fuel filter that looked just about as bad as everything else under there.

That encounter was a victory — time, chance and entropy had done their best to render this vehicle undriveable. But with some of our time, we undid enough of the entropy to hopefully remove chance from the equation.

Article Details

Fri, 06/01/2018 (All day)

Richard McCuistian

<p>Time and chance work both ways &mdash; customers need us, and we need them. Here&#39;s series of vehicles &mdash; and their owners &mdash; in need of help and repairs.</p>

<p>auto repair, Richard McCuistian, diagnostics</p>

I was recently called to a shop on a 2012 BMW X5 with a 3.0 Liter Engine (Figure 1) that needed a new Engine Control Module (ECM) programmed. The shop had determined that the ECM was internally damaged and needed to be replaced. They purchased a new ECM from the dealer because a used one would not work on this vehicle due to the fact that BMW will not allow it. Most manufacturers have a procedure to overwrite the Vehicle Identification number and realign the module with the onboard Vehicle Security System but that is not the case with BMW. Their Engine Control Modules are a “One-Time” marriage and it is required to purchase a new ECM from the dealer only.

Figure 1

When I arrived at the shop, I needed to see for myself how the shop came to the conclusion that the ECM was damaged. This can usually be determined by a visual inspection or by a simple “smell” test for any signs of a burnt circuit board. Just going on an assumption can be VERY costly if you are wrong in your diagnostic process so I needed to make sure the shop was headed in the right direction. It would be a bad situation if I was hired to program a control module and the vehicle ended up with the same results as the old one. I was hired as a salesman to stuff software and a configuration file into the ECM, and though I wear many hats, my “technician” hat was not the one I was wearing today. However, I could always be hired later to diagnose the vehicle if needed. So I did as I was told and kept my fingers crossed.

This is new!
The head technician in the shop did assure me of his findings by letting me see for myself what he had found prior to me starting the programming procedure. He pointed out a pile of damaged components (Figure 2). I was taken back by his findings and the amount of damage involved on this vehicle. This vehicle uses an electric water pump that had failed. It had basically burnt up and took out components in its path of destruction. By taking a closer view of the water pump (Figure 3) you could see the damage the water pump caused to the water pump connector.

Figure 2

Figure 3

The shop simply replaced the water pump and wired a new connector end to the existing harness but the vehicle did not run very well and was setting a few running codes for Injectors and ignition coils. When the technician did further diagnostics he discovered a burnt connector at the ECM (Figure 4) and he had no other choice but to replace the ECM along with a sub harness for the ECM. What a chain reaction of events for a simple water pump replacement job after the owner of the BMW drove the car to the shop complaining about a CEL lamp on, burning smell from the engine compartment and a vehicle that was not running well.

Figure 4

I liked it better in the old days when a water pump was simply driven by a drivebelt. If the water pump went bad you could easily remove it from the engine and overhaul it on the bench by replacing a bearing that usually failed. That operation now is no longer practical and requires a complete replacement with a new or rebuilt water pump. Then there is this new wave of technology where they want to be rid of the engine carrying too much of a load, driving many components so why not an electric water pump that can be controlled by varying speeds of operation or even turned off when not needed. But I always say that there is always a price to pay for new technology until they get it right.

Okay so now I go through the long process of programming the ECM, making sure I maintain a specific charging voltage between 13-14 volts. On most vehicles if your charging voltage is not maintained within the specification the operation will self-abort if the voltage is too low or too high so it is important to use a qualified battery charger that has a programming feature that will maintain the voltage even if a current surge occurs such as a coolant fan coming on while programming. You don’t want to lose the ECM in the process or it will be your responsibility to purchase another ECM if the parts guy is unwilling to cover you on your mistake. Most electrical parts cannot be returned and it becomes a tug of war with the parts guy who will interrogate you to make sure you claim ownership of that part that will end up hanging on your wall as a memory.

Programmed, but not running?
I finally finished my programming task and I go to start the vehicle and it will not start. This seemed odd to me because I had followed through on all the step-by-step procedures without skipping a beat. The technician was even looking over my shoulder as I was doing the job and we looked at one another in disbelief. Then came these words out of his mouth, “The car was running before with the old ECM.” This remark was insinuating that I did not program the ECM properly but I have done many BMW control module installations and was very careful in the process. So now this vehicle had me second guessing myself and I sat there scratching my head as to why the vehicle would no longer run with the new ECM Installed. Now it was time to put on my “technician” hat and remove the “salesman” hat and go to work.

Figure 5

I scanned the entire vehicle to get a complete overview and recorded the codes in each control module. I next cleared the entire vehicle to see what codes would reappear. Keep in mind that during the programming process it is normal for many controllers to set codes when the ECM goes offline while being programmed. When I attempted to start the vehicle it still would not start after a few key cycles and cranking attempts. I proceeded to communicate with the ECM and scan it for any new codes. The good news was that the ECM was alive and well, but it had a few current codes in memory (Figure 5). The ones that caught my attention were codes 2A61 (Relay, Ignition and Injection system, supply voltage, fuel injection: Line disconnection) and 387F (Power management: Standby current violation). Without even having to read documentation on these codes and using my common sense diagnostics these codes were directing me towards power feed issues for the injectors and ignition coils. I now had to look at wiring diagrams to make sense of it all.

Figure 6

By looking over system diagrams I discovered that these injectors and ignition coils were not feed power directly from a fuse but rather through power drivers internal to the ECM. This Engine Control Module had the ability to control both sides of the injectors and ignition coils but the ECM was fed power supply for these drivers from an integrated relay module assembly that housed the ECM main, Injection/Ignition Coil and Valvetronic Relays (Figure 6). This Integrated Relay Module was not located in an easy access area but rather buried deep below the windshield, in the right side cowl under the passenger cabin filters (Figure 7). I’m thinking that this would be a bad location to stick electrical items especially if any water coming down the windshield would breach its normal travel to the base of the windshield and out the drains provided in the cowl.

Figure 7

I located the Integrated Relay Module at the base of the cowl well (Figure 8) but I needed to remove the module from its location to get better access to testing all the wires. By doing this I unfortunately had to unplug all the connectors and move everything up out of the lower cowl. To my surprise I found that the module connections were all corroded from moisture (Figure 9). This was probably due to a prior water leak by the looks of all the leaves at the base of the cowl housing. This poor BMW owner was not having much luck with his car because now he was looking at another part that had to be added to the list and hopefully the harness connectors could be salvaged without replacement.

Figure 8

Figure 9

But wait! There’s more!
When I removed the module from the vehicle and it was in my hand my human sensors kicked in. I smelled something that I was accustomed to that had that sweet smell to it. I took a closer whiff at the module and it smelled like antifreeze and it was not water at all. All of a sudden a light went off in my head and I cracked the case! This vehicle was exposed to “Automotive Intravenous.” Something I have not seen in years! When the water pump burnt the connector the plastic housing was compromised and allowed coolant under pressure to force antifreeze through the engine harness. The antifreeze worked its way back to the ECM which was located under the intake manifold and caused damaged there and then the antifreeze took another journey down into the cowl and trashed the Integrated Relay Module. Wow!! What a turn of events!

I basically sat there for a moment because I was mesmerized by this whole situation. You just never know what you will come across in this automotive field of diagnostics and all you can do is keep an open mind and be alert. Don’t be the one wearing headphones and listening to tunes while working on a car because you will miss out on all the experiences you need to gain using the sensors you were given at birth. My only hope is that this article has opened your mind and hit home with some of you techs out there.

Article Details

Sun, 07/01/2018 (All day)

John Anello

<p>If you&rsquo;ve been around a while, you&rsquo;ve seen cases where fluids would travel up wiring harnesses to other components &ndash; often well away from the source of the fluid. Bet you&rsquo;ve never seen one like this, though!</p>

<p>BMW X5, ECM, reprogramming</p>

I’ve been in this business since the early seventies, and the guys who are my age and older know that there was a time when the most complicated electrical issue we might encounter on a vehicle would be turn signals or power windows. Even back then things happened that didn’t seem to make sense.  I encountered a ’78 Dodge pickup with an inoperative left-hand turn signal – after checking bulbs, wiring, grounds, etc. I discovered that simply replacing the flasher brought both sides back online.  Never quite understood that one.

Then there was the ’66 Cadillac convertible with a driver side power window issue that would come and go, and as I dug into that one I found a pushed back pin in a connector at the left kick panel – and from the condition of the harness and the connector it appeared that it had been that way since the car was brand new.

Once my brother’s 78 Cadillac developed road-speed radio static that he only noticed after the tires were rotated; back in those days you weren’t supposed to cross-rotate radial tires, and while I was digging in the dash for issues with the antenna and whatnot, he noticed from looking at his spoke rims that the tires had indeed been cross-rotated – and when we put them back like they were supposed to be, the while-driving radio static evaporated.

Then there was the 80 model Lincoln that would buck and skip exactly five minutes after a morning cold start but would never do it again while the car was warm – and that turned out to be a pushed-back wire in the crank sensor connector pigtail. I can’t explain the five-minute deal, but when I seated that connector the problem was gone.

I knew of one six-volt vehicle from the ‘50s that wouldn’t spin and wouldn’t start with the key but would instantly fire up if you put it in gear, pushed it, and popped the clutch. That one turned out to be a bad engine-to-frame ground.

Headlight issue

This little old S10 had a lot of other issues that had been ignored until it developed a headlight issue, and if somebody’s planning to drive at night or in the rain, the headlights are a must-have.  Initially, I was thinking this would be a slam-dunk.  How hard could it be to figure out a headlight problem on a 15-year-old domestic?  Well, we hadn’t tackled one of these S10 headlight issues before, and this one was a wakeup call.

Drawing a headlight job on a truck this old would seem to be a simple exercise.

The initial concern was that the headlights tended to only illuminate on flash-to-pass. Occasionally they would work normally, but usually they wouldn’t. Heck, the Daytime Running Lights wouldn’t even work.  The owner of the truck couldn’t care less about the DRL, which isn’t required in these parts – he just wanted to turn on the light switch and see where he was going at night.

To begin with, I like to see if power and ground are available at the bulbs with the circuit energized, and as we traveled that path, we got side-tracked when we found that we only had ground at the right front headlamp – with the bulbs unplugged, there was no ground at the left front lamp, but with the right front bulb connected, we had a ground. This tended to confuse the student I had doing the work, and so we waded into the wiring schematic – which became even more confusing. Folks who are familiar with this platform are already smiling, I expect.

(click image to enlarge) This schematic is confusing on several levels – note that there are two daytime running lamp relays shown – and one of them parenthetically mentions an RPO code, but the other one simply says “domestic.” The headlight grounds exit the first page going down and enter the next page going up. The ground that passes through the headlight grounding relay begins on the bottom and goes north through the relay and then enters the page in the middle headed south through the Multifunction switch. Complicate that by shoving the grounding relay into a panel ‘way up under the dash and you’ve got a recipe for frustration. Rather than trying to contain all this on one schematic, they should have provided a different one for non-domestic vehicles.This is ridiculous.

One of the maddening things about so many of today’s schematics is how they move from page to page with those funky arrows. Granted, the shop manual folks sometimes give us link boxes on those arrows so we can jump right to the page where the circuit continues, and that’s a good thing.  Gone are the days when the entire vehicle schematic could be found on just one page (of course, that was in the 1960s).  This schematic was light years away from that one-page utopia, and besides all that, it broke some key rules.

I teach my people that, in most cases, on a schematic, power comes in from the top and ground comes up from the bottom of the diagram.  And that’s usually the case, although I’ve seen it violated a few times on isolated schematics for one reason or another. Well, this S10 schematic shatters that rule and inserts some other curve balls in the process.

The origin for the ground was G200, which is under the dash in front of the driver and attached to the bulkhead. That ground feed makes its way through a splice pack to feed a lot of other stuff, but for our purposes, it feeds the headlamp grounding relay through the common and normally closed terminals in that relay. The ground then departs that relay, makes its way to the multifunction switch (from the top of the diagram, no less), and the MF switch feeds it to the headlight bulbs, which are powered by the headlight relay.  As the ground feed departs the MF switch the ground passes through the under-hood fuse block (no fuses in this ground circuit, though) and then exits and splits into four different feeds – all of which exit the page headed south – i.e., toward the bottom of the page – which no ground circuit should be allowed to do (my opinion).  When these grounds reappear feeding the headlamp bulbs, they enter the page from the bottom (as grounds are wont to do).  Since they exit the previous page headed south and enter this page headed north, the student wound up in a tailspin, effectively auguring her troubleshooting plane down into the slough of no understanding.  It was a nasty thing to watch and even nastier to experience, since I was in the copilot’s seat trying to teach her to fly.

Homing in on the target

Understanding the circuit and being able to locate and access the various connector and components is of obvious importance. In this case, the components consisted of the headlight switch, the BCM, the headlight relay, the headlight grounding relay, and the Daytime Running Lamp relay.  The BCM is a major player here, receiving a Headlights OFF signal from the headlamp switch, which, through another part of its ganged array, sends Headlamp Relay Coil power to the BCM so that the BCM can operate the Headlamp Power Relay at its discretion with the switch in the ON position. So, the Headlamp switch, through two different circuits, sends power AND ground to the BCM. 

The BCM is monitoring ambient light by way of an electric eye on the right side of the dash for DRL activation when the other conditions are met.  Both the DRL and the Headlamp grounding relays are feeding the lamps through their normally closed terminals so that when the headlamp power relay is energized, the left headlight is forced to get its ground through the right-hand headlight bulb’s filament – in a word, the headlights are illuminated in series during DRL operation and are only half as bright, rather like the cooling fans that are fed in series when they’re spinning on low. The schematic shows an alternate wiring of the DRL relay if the vehicle isn’t “domestic,” and that doesn’t help a new schematic reader either.

Flash-to-Pass is a separate switch within the MF switch that triggers the BCM to energize both the DRL relay and the Headlamp grounding relay.  The Headlamp Grounding Relay then breaks the circuit to ground and the DRL relay grounds the left headlamp directly, bringing both headlights into a parallel circuit situation for a bright Flash-to-Pass. This is also supposed to happen when the regular headlights are on at night. This wasn’t happening except on Flash-to-Pass, and that was the concern we were pursuing.

Dash-digging and ground-checking, we finally managed to find a bad multifunction switch by checking the ground feed that was supposed to pass through the switch but didn’t.

So we decided to back up and take another run at it. I always teach that circuit checks are best made at the easiest accessible point, no matter where it may be in the circuit, and to work from there. The annoying thing about this truck is that the Headlamp Grounding Relay is in a relay center that is mounted in a very tight spot under the dash on the left hand side, which makes the relay no fun to access. So we began at an easier spot.

Noting that the normally closed Headlamp Grounding Relay contacts feed the ground circuit to the MF switch pin E13 by a yellow wire, we determined that there was indeed a ground at the MF switch but that it wasn’t passing through the switch to the lights.  Ground in – no ground out, not on pins E12 OR E11. That was something of a breakthrough – and when we bypassed the switch, we had lights.  And so I had Kayla replace the Multifunction Switch, the lights worked, and everybody was happy. It was a wild ride, though.            

Transfer case complications

This was a 1997 Tahoe that came in with a rumbling driveline noise, which turned out to be a leaky transfer case that had gone dry and had destroyed itself internally. They had driven the vehicle like this for a while, opting not to do anything about it until the noise became more troubling. The initial complication came from the salvage yard; the first transfer case to arrive was the wrong one.  We had already removed the old transfer case, which was quite a job, since the torsion bars and their crossmember had to be removed and not much of anything had been disassembled on this one for years.  But we made it happen. And when the correct transfer case came in, it looked clean and dry and was the right part, and so we popped it in, put everything back together, and pumped the requisite amount of Dexron II in there. We also replaced the output shaft seal on general principle.  And then came the complication. We drove the vehicle and heard no noise, but when we looked underneath, the replacement transfer case seemed to be leaking the same way the original one had – between the case halves.  So that one will have to come back out for a re-sealing.  I guess we need to devise a method of pressure-testing it before we put it back in there.

This one kind of reminds me of a transmission swap we did on a four-wheel-drive Expedition a couple of years back that did famously for about a month and then came back with a cracked flywheel.  It was like having to do the whole job all over again.

On another note, a 1999 F150 came in with a ruined rear end due to failed pinion bearings (it had been driven that way for quite a while) and we snagged a replacement rear axle from the same salvage yard for five Ben Franklins. The brake backing plates were banged up on the salvage yard rear axle, and we had to swap and replace a lot of the brake parts to get the rear disk stoppers done right, but that job went like a song.

The pinion gears in this differential had died and it had been driven enough to mark the carrier pretty heavily. Rather than buying the parts to rebuild this one we just got a replacement. That repair went smoothly.

Ignition quickies – and a complication

There are two of these I’d like to share. One was a 2003 Suzuki XL-7 that came in for an exhaust leak. We found that somebody had started trying to cut the exhaust (to steal the cat, maybe?) but had decided to stop only partway through. After I fired up the torch and coat-hanger welded the exhaust leak shut (we don’t have a wire welder, although we should have, I guess), it became evident that the engine was skipping to beat the band. The driver hadn’t even noticed the skip!  Rather than busting out the scan tool, I grabbed the GTC505 and rested its wand on the top of the coils until I found a high firing voltage on one coil. The plug was new but greasy and we popped a new plug in its place. It took about thirty seconds to locate a bad spark plug and another five minutes to replace it and that skip was history. We also checked the compression on that cylinder and rechecked the spark pattern after replacing the plug, and we cleared the codes with the Autel.

Using this method, we found the Suzuki engine skip (right) within thirty seconds, never having even connected a scan tool. This provides a much higher resolution peek at the ignition system than simply yanking the P030x code and was a LOT faster.

The second ignition quickie was on a 2009 Camry that had developed an engine skip on #1 and had tossed a primary ignition fault code for coil A. The problem was that, while the skip had been dead and present for many a mile, it stopped happening about the time the Camry made it to the shop, which is, as we say, par for the course.

Since the GTC 505 was just lying there in its open box after the other job, I grabbed it to see what the pattern looked like and found that the erstwhile misfiring coil’s pattern didn’t look out of line – of course, the engine was running smooth, too. Nevertheless, I ordered an aftermarket replacement coil from the parts store and installed it, along with a new set of plugs, because this one hadn’t had any and it was only a few miles early according to the maintenance schedule. It still ran smooth, but when I checked the new coil with the 505 I saw an astonishingly high voltage – about 90,000 volts.

I reinstalled the original coil and saw less than 20k, which was what the other three coils were reading. I called the parts store and had them send a different brand of coil, and when we installed that one the pattern was normal.  Then the parts store manager told me that the manufacturer of the first coil had said that Japanese cars require a higher voltage coil and that we had possibly wound up with one of those – not sure what to make of that information, but oh well.

The Camry was an adventure, to be sure – and we never would have known the replacement coil wasn’t right had we not verified the firing pattern after we installed it. Don’t know about that business of Japanese Camry coils needing a hotter spark – but I wasn’t about to let this sleeping dog lie.

The lesson I gleaned from that Camry experience was that it’s wise to double-check after installing the new part – you know, trust but verify? It was a satisfying element of “verifying the repair” that went beyond a simple test drive.  After replacing the coil the first time, the Camry was running so well that I would have had no reason to suspect foul play had I not done an after-check with the 505 just for grins.  Both ignition jobs went a lot smoother and a lot quicker than they would have if we had used only a scan tool.

Then there was the Pontiac Power Loss issue – after we had exhausted scan tool diagnostics on that one, we screwed my homemade pressure test fitting into an upstream O₂ sensor hole and found enough backpressure to condemn the cat. We replaced it with a Walker bolt on replacement. It was a fitting end to a satisfying week.

Article Details

Wed, 08/01/2018 (All day)

Richard McCuistian

<p>How hard could it be to figure out a headlight problem on a 15-year-old domestic? Well, we hadn&rsquo;t tackled one of these S10 headlight issues before, and this one was a wakeup call.</p>

<p>auto repair, S10, headlight repair, wiring diagram, transfer case</p>

This diagnosis begins like many others have in the past. The local guy from the used car lot drags in a "great deal" he picked up at the auction. You know the vehicles — clean, southern, low mileage, and (oh yeah!) it doesn't run! This time it happened to be a 2008 Jeep Liberty 3.7 brought in on the trailer. It would crank and attempt to start, smelt heavily of gas when it did run, accompanied with a heck of a lot of mechanical noise from under the hood. Prior to dropping it off the throttle body was replaced as well as the intake manifold gaskets and spark plugs. However, now that it is at our shop it is time to see how much of a "great deal" this vehicle really was.

Figure 1

Now that the vehicle is in the bay it is time to get to work. Where to begin? I initially scanned the vehicle for codes to see if there was anything that might help give some direction. There were approximately 12 codes stored in the ECM, but at first glance none of them seemed to be of any value for the current situation. (Figure 1) It was obvious when I pulled the vehicle in there was a hard misfire on one or more cylinders, along with a fair amount of popping and mechanical engine noise, so I made an attempt to use scan data to see what cylinder(s) were having a hard time but at this point I was not able to get the vehicle to run long enough to gather any useful data. Seeing that gathering scan data was not going to be an option it was time to move on.

Figure 2

The next step in my diagnostic routine was to set up my Pico scope and run a relative compression test on the engine to gather a "general health check" of the engine. With the heavy amount of mechanical noise, you could hear when the engine did run, I figure this would be the best next step. Often times the relative compression test can give us an insight to the cylinders’ ability to seal and show us how they are in comparison to each other. I am sure if you have used this approach you are familiar with the classic waveform and the benefits it can hold. After disabling the fuel pump and unplugging the ignition coils, I clamped my high amp clamp around the battery cable and set up a trigger on the #1 ignition coil (Figure 2) Now we are ready to crank the engine!

Figure 3

This is where we gather our first bit of usable data and direction. Have a look at the waveform we gathered and tell me what you see. (Figure 3) The blue trace is our starter current and the red trace is our #1 ignition coil trigger. Quickly we can see that the ignition timing seems to be about right occurring just before TDC. Ok we can put that in our memory bank. Let's focus on the starter current now. At first glance, on the starter current waveform, we might think there are two "good" cylinders (the higher humps) and perhaps three other cylinders that are not contributing as much (the lower humps.)

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But before we draw any types of conclusions based on this let's have a close look at the amperage scale (Figure 4). We can see that the amperage draw of the higher humps is near 300 amps! Experience will kick in at this point and tell us that "normal" starter current draw is around 150 to 200 amps on these engines. After observing this the big question becomes, how can the starter draw too much current? Can a cylinder have too much compression?

Figure 4

Figure 5

After some pondering and knowing that these 3.7's along with the 4.7 liters are notorious for the cam followers (rocker arms) falling off, can we make a hypothesis based on this data as to what might be going on in this engine? After all we are trying to gather as much data as we can before we open it up. Knowing the firing order 1,6,5,4,3,2 and knowing the companion cylinders 1 and 4, 6 and 3 and 5 and 2, could this help us (Figure 5)?

After a few moments, a cup of coffee and some pondering I came up with the conclusion that if #4 and #6 exhaust valves were not opening then it would appear on the relative compression test that the #1 and #3 were doing extra work on their compression stroke. Make sense? So let's say the #1 cylinder is traveling up on its compression stroke and starting to draw current from the starter. At this same time the #4 cylinder is on its way up on the exhaust stroke. TECHNICALLY this should not affect the starter current because the exhaust valve is open. But what if it wasn't? In that case it would be building compression in #1 AND #4 drawing near twice the current as normal from the starter. Same goes for cylinders 6 and 3.

Figure 6

Now that we have a pretty darn good idea what could be happening and we know what two cylinders are the potential culprits, can we prove this 100% before pulling out the wrench set? The easiest way I figured would be to use the Pico and an in-cylinder pressure test to prove or disprove our theory. It should be pretty easy to identify a nonfunctioning exhaust valve with the pressure test. I started on cylinder #4 and there it was (Figure 6)! 180psi compression and 150psi compression on the exhaust stroke of the engine! It did not take long to move the transducer down one hole and see the same exact waveform on the #6 cylinder. This made the diagnosis 100% complete. The #4 and #6 exhaust valves were not opening. On a side note, what would you have seen if you were using a regular compression gauge? 180psi? Would you perhaps have moved on at that point, assuming the cylinder was good? Always keep in mind that the standard compression test only shows the cylinder’s ability to seal, not breath. This is where a pressure transducer and a scope can really shine over a compression gauge.

Figure 7

Data has been gathered, pondered and proved so now it is time to get dirty. Fortunately for us both 4 and 6 are on the same bank so we only had to pull one valve cover. As soon as the passenger valve cover was removed both exhaust rocker arms were found laying on top of the head (Figure 7). Ahh, the sweet feeling of victory! I discussed with the used car lot as to my thoughts on what causes this and what the corrective action should be and you may know how this ends. The rocker arms were snapped back on, valve cover reinstalled and it was off to the sale! The customer was happy that he really did get a "good deal."

If you take anything away from this, I would hope it would be that sometimes we need to slow down to go fast. Gather as much data as you can before tearing into an engine and take the time to look at the scales on your relative compression test and not just the overall picture because as we proved sometimes and engine can have too much compression!

Article Details

Sat, 09/01/2018 (All day)

Eric Obrochta

<p>Many drivability concerns are related to engine mechanical conditions. Check for these first before you spend too much time playing with ignition or fuel issues!</p>

<p>drivability concerns, auto repair, Eric Obrachta, Jeep Liberty, intermittent start</p>

With the proper training, the correct tooling and a thorough understanding of how our opponent (the subject vehicle) “ticks,” the odds are high that the fault can be identified, the root-cause pinpointed, and vehicle repaired in a reasonable amount of time. That is, of course if we can identify what the customer is concerned with.

Lesson #1 – The three-legged stool

I want to take a moment to bring up a very valuable lesson I learned years ago from AutoNerdz founder Tom Roberts. Tom is an invaluable contributor to the automotive industry and is known for his diagnostic and scope expertise. He once described the ability of a technician to perform his/her duties as being perched upon a three-legged stool. The three legs represent a technician’s competency, capable tooling and adequate information.

I believe Tom used the analogy because, just like a three-legged stool missing a leg, a technician who lacks one of the three items would soon find himself toppling over in a crash-landing. We must fortify ourselves from those three angles to be consistent and successful diagnosticians and technicians.

Lesson #2 — The 85/15 rule

There is another valuable lesson that I was taught years ago. About 85 percent of every action that occurs on an automobile, occurs on all of them because it must. It is a matter of physics. For example, we can energize a fuel injector by completing the path to ground, by providing a voltage source or even by providing both a voltage source and ground path. The point is the injector must open to allow a cylinder to be fueled properly. The 85 percent is that very fact…the 15 percent is how the manufacturer designed that function to be carried out. This very lesson is the basis for this topic of discussion.

The initial encounter

The vehicle in question is for a very loyal fleet account of ours (Figure 1). It seems their 2013 GMC Sierra Diesel 6.6L (LML) with 186K on the odometer has been experiencing a loss of coolant level for some time now. I was issued the vehicle for evaluation along with some basic routine maintenance. The vehicle was well maintained and in fine shape. I noticed the degas bottle exhibiting a very low level of coolant and in the engine compartment the unmistakable, sweet smell of hot antifreeze lingered over the hot powerplant. A visual inspection of the hoses was carried out and the leak was easily pinpointed to the lower radiator hose. I received authorization from the fleet manager to complete the repair and the vehicle was ready for pick-up later that same afternoon.

Figure 1

It was about 3 p.m. when the driver of the truck returned to the shop to retrieve the vehicle. He was excited to get his truck back but left me with some concern when I met him in the parking lot. It seems the driver had failed to mention upon drop-off that he was experiencing some difficulty starting the engine from time to time. I certainly noted no such symptom each time I started the truck and I asked him if he could demonstrate the erratic behavior for me. The driver attempted to duplicate the strange concern but to no avail. The truck’s engine repeatedly started without hesitation or struggle. I reassured him with visual confirmation of the battery’s condition, as I had left (on the passenger seat of the truck), a print out of the starting/charging system test we perform as a courtesy during routine maintenance. Satisfied, he took the vehicle and assured me that he would return if the symptom were to present itself again.

Lesson #3 — The interviewing process

Sure as can be, the following Monday, the driver returned to the shop with his truck and a complaint of the hard-start concern. This time I asked him to spend a few minutes with me so that I might ask him a few questions regarding the nature of this erratic fault. In my experience, it’s always been a fantastic idea to interview my customers on the nature of the faults and for good reason. Just think how often an intermittent fault arises. We call it intermittent, but the fact usually is that once we figure out how to force the fault to reveal itself we can almost do so at will. Intelligent questions regarding failure criteria include asking about weather and ambient conditions present at the time of the fault, whether the vehicle had experienced a hot or cold soak prior to the fault, the frequency of the fault and overall driving habits.

These can really help narrow the failure down and eliminate a lot of wasted time and energy. After speaking with Ron, the driver of the GMC, it has been determined that the symptom is only exhibited if the truck sits all day after a drive to operating temperature. I asked Ron to then describe the symptom to me. What does he mean by hard start? He responded by telling me, “The engine seems to stutter while its cranking over, like perhaps the starter is failing.” That description brought a thought to the forefront of my mind and I didn’t like what I was seeing. His description of the starter operation led me to believe that the engine became difficult to turn at some point in the 720-degree engine cycle. I do want to reiterate, that the truck was very well taken care of and was relatively young, especially for a diesel powerplant. The thought of a potential mechanical failure didn’t sit well with me but the clues I have before me will lead me down that path for initial testing.

Lesson #4 — Returning to my roots

As mentioned earlier, the 85/15 rule regards mastering the function and operation of all that apply to the 85.

Being intimately familiar with engine operation, engine management systems as well as their components and their functionality, give us the ability to apply testing techniques to monitor their functionality. Because these devices apply to every year/make/model on the road, it’s only beneficial to invest the time to master them. Which brings me to my next point.

Lesson #5 — Test known-good vehicles

I’m not a diesel tech, and though I’ve worked with them successfully, I don’t currently possess the experience necessary to be comfortable with them. They require me to remain extra focused as they don’t present to me as second-nature like they do to more experienced and properly trained diesel technicians. What is neat about the approach to this diagnosis is that I don’t need to be a diesel tech! I know DC motors and what to expect to see on a lab scope to determine whether they’re operating properly or not. I’ve learned years ago to carry out testing techniques on known-good vehicles. Being comfortable with what “GOOD” looks like means “BAD” sticks out like the proverbial sore thumb.

Figure 2

Because of the fault description Ron provided me, as well as the way the fault presented itself, it led me to believe that the engine was the cause, becoming difficult to turn somewhere in the 720-degree engine cycle.  I was going to capture the fault using a lab scope and a high current amp probe while operating the vehicle under the same failure criteria Ron had described earlier.

If you refer to Figure 2, you can see a capture of starter current, while cranking a known-good vehicle. This trace first exhibits an in-rush current. This is the tall peak you see to the left of the capture. What this represents is a momentary high rate of current flow. This occurs because the starter uses a lot of energy to get the engine moving. Once the engine begins to rotate, the energy required to keep it rotating has diminished. Next you will notice the repetitive peaks. The represent the Top Dead-Center (TDC) locations of each piston’s compression stroke, in turn. The waveform presents in this fashion because the starter consumes more energy trying to compress the contents of the cylinder then it does simply rotating the crankshaft (Figure 3).

Figure 3

Flushing out the fault

The GMC was taken on a road test around town for about 20 miles to get the big 6.6L up to operating temperature, just as Ron described. The vehicle was then parked for the rest of the afternoon and was prepped to capture the fault, red-handed, first thing the following morning. I placed a 600A-rated current clamp around the heavy cable feeding the starter motor.  Although it may not have been totally necessary, I chose this test location to eliminate other devices that will serve as “noise” in my starter current capture. Devices like fuel supply pump and glow plugs may impede upon my capture and hide what I was trying to see.

I connected my current probe to my lab scope and zeroed the probe out. I turned the key and awaited the extinguishing of the glow-plug indicator. I then cranked the engine over and found the description Ron provided to be totally valid. On top of that, my lab scope reflected the fault as a momentary event of high current draw, indicating a high starter effort was required.  Unfortunately, the capture was inadvertently erased and I had to repeat the prep-process with only a couple of hours allotted for me to capture the fault for this article. If you see Figure 4, you can see the second peak from the left is not like the known-good example displayed. It represents the starter momentarily struggling before it continued to rotate.

Figure 4

Because this only occurs upon the initial cranking of the engine, it’s an indicator that the engine is likely trying to compress a liquid in one of the cylinders (fuel, coolant) rather than a mechanical fault internal to the engine, as this would likely be more prevalent. I will point out that that there is no visible smoke once the engine is started.

Who’s the culprit?

I always let the results of my easy tests drive me to more pinpointed tests. This way, every move I make is justified. Every subsequent test will yield an answer. There is no shooting from the hip, so to speak. I also always curtail my testing around the configuration of the subject vehicle. In most cases, I would like to prove (as easily as possible) which cylinder is at fault. In this case, I already know that the fault is going to be time-consuming to repair and I just must see what fluid is filling one of the eight cylinders. This piece of information will determine what the repair will be and how far the vehicle will have to be disassembled for repair.

Figure 5

I chose to remove all eight glow plugs. They are very easy to remove and because they plug directly into the combustion chambers, the removal will yield me the information I seek. The engine was once again ran hot and put away for the evening. The glow plugs were removed and the engine was cranked over. If you refer to Figure 5, you can see a still-capture of a short video. It is showing cylinder #6 expelling coolant from the glow plug port as the piston ascended towards TDC.

Pinpointing the root cause

After gaining permission to begin disassembly of the 6.6L, it was noted throughout the disassembly process that no other components outside of the combustion chamber were wet with coolant. This further corroborated the thought that the fault lay internal to the combustion chamber of the suspect cylinder or at least common to only the suspect cylinder. The cylinder head for bank #2 was removed for inspection and a crack in the coolant jacket within one of the #6 intake valve ports was found to be the root-cause of the “hard-start” concern (Figure 6). The takeaway from all is that a solid foundation of basic testing techniques is what it took to gain a diagnostic direction. One doesn’t have to be a “specialist” of any particular make or model to be successful in performing the diagnosis – but having a solid foundation, capable tools and adequate information is key to keeping your diagnostic balance on the three-legged stool!

Figure 6

Article Details

Mon, 10/01/2018 (All day)

Brandon Steckler

<p>As technicians, we are faced with jobs or situations that challenge our abilities. Do you have the right strategy, tools and attitude to tackle them?</p>

<p>auto repair, vehicle diagnostics, Brandon Steckler, Motor Age,</p>

When we think of failures, we often thing in terms of components since most of the time, that is what ends up being replaced especially with ignition problems and crank no-starts. Often times we overlook or never consider something that is becoming more common and that is the terminal contact inside of the connector to a component. The intermittent nature of terminal connection problems make them extremely hard to diagnose since they often occur so fast and also so randomly. One technique is use an oscilloscope to help pick out quick glitches in a circuit that would be hard to locate with other testing methods.

2013 Dodge Durango

The first vehicle is a 2013 Dodge Durango with a 5.7L engine and 52K miles on the odometer. It was towed in with a complaint of a crank-no start. The customer stated the vehicle has been running rough and had low power before it stalled. When I went outside to try to start the Durango, it started right up like most technicians have experienced with a vehicle that was towed in and as most technicians would, I instinctively thought that a fuel pump was going out.  Something else that I noticed was I could not shift out of park, but after repeatedly pressing the brake pedal the shift interlock released so I could move the vehicle.

The 2013 Dodge Durango with a 5.7L engine

When I went to pull the Durango inside it died out while making a turn. I noticed a long crank before it restarted, then after about 20 feet it stalled again and this time it would not restart. After getting some help to push the vehicle in my bay, you guessed it; it started up and idled fine. Ok, let scan the vehicle for codes and take a look at some data before testing the fuel pump. I found a stored code P0627 Fuel Pump Relay Circuit which seemed in tune with the stall and long crank that followed afterwards. Also stored was a P0571 Brake Switch Performance code which explained why I have difficulty shifting out of park.

A good first step is retrieve Diagnostic Trouble Codes (DTCs) that give some direction in deciding where to begin testing.

Shortly after the vehicle was inside the service writer came with some information that the customer has shared with them. The customer informed us that the vehicle had been brought to the dealership earlier in week to have a fuel pump relay recall performed. They only had it back for a day when the stalling started occurring intermittently and then last time it stalled, it would not restart, only crank. We were also informed that prior to being at the dealership for the fuel pump relay recall repair, they did not experience any problems.

The fuel pump relay was originally an integral part of the TIPM, but when the safety recall has been performed, it is visibly mounted on the right front of the engine compartment.

On these vehicles, the fuel pump relay is integral to the Totally Integrated Power Module (TIPM) and is not serviceable separately. It appears that the fuel pump relay is problematic and a recall had been issued for this vehicle. Safety Recall R09/NHTSA 15V-115 addresses this problem, but instead of replacing the entire TIPM assembly, the repair is to rewire some of the TIPM circuits and add an external fuel pump relay.

After getting this information I focused in on the fuel pump relay to find out if anything during the repair was left loose. I printed a copy of the recall repair instructions so I could familiarize myself with the procedure and hopefully narrow down the number of circuits to test. The connectors of the Totally Integrated Power Module are secured by a flip type lock to hold them in place so there was little chance of them not being pushed in fully. Most of the repair consisted of cutting and splicing wires of the fuel pump circuit going to the TIPM into the harness supplied for mounting the fuel pump relay remotely from the module. The repair passed a visual inspection so I attached my oscilloscope to the each of the relay circuits to determine if one of them was causing a loss of voltage to the vehicle’s fuel pump or if I need to look elsewhere.

Since the relay is mounted remotely, it made an easy test point to start looking for a problem related to the DTC and no start concern.

The location of the relay on the fender made an easy point to attach my scope leads to get direction on what is and is not working as designed. Just a heads up, if you open the hood on any of these vehicles that were affected and there is a single relay attached to the right corner of the engine bay held in by a push clip, the recall has already been performed on that particular vehicle. By attaching to the fuel pump relay I could monitor whether the PCM was commanding the relay on and also what the output voltage to the fuel pump was when the vehicle was either cranked or running. It so happened that when cranking the Durango that this time it started and kept idling. As seen on the scope capture, the green and red traces showed a lot of drop outs, which corresponded to the PCM control circuit commanding fuel pump relay on and off and the output from the relay to the fuel pump respectively. The rapid on/off of these to signals continued until the vehicle stalled out.

Reviewing the capture, I found that the Green trace which is the relay command from the PCM was the dropping out first, following closely by the Red trace, which is the voltage output of the relay to the fuel pump.

Monitoring each circuit of the fuel pump relay it didn’t take long to find a problem in the relay control circuit.

Zooming in on the capture we can see that the control circuit from the PCM is losing its signal which in turn is causing the fuel pump relay to open and causing a loss of voltage supplied to the fuel pump.

Reviewing the procedure involved to install the external fuel pump relay, I found that the relay command signal was spliced into a Pink wire with a Green tracer, which goes to Pin 38 of a 40-pin connector at the TIPM. Lifting up the TIPM and inspecting the wiring did not reveal anything loose. The brass splice band and solder joint where the relay wiring attached to the original TIPM wiring also showed good. Inspecting the pin fit in the connector revealed something else. After the technician removed the terminal lock from the 40-pin connector, he must have used an incorrect tool to push the terminal out of its cavity because the terminal was spread and there was no grab felt at all during the pin drag test. As seen in the picture, the terminal flopped around when inserted over the mating male pin. This was the poor connection that was causing the vehicle to stall out when driving or when slight movement of harness existed.

A close up of the spread open terminal connector causing a poor connection at the TIPM.

Since the external fuel pump relay and related wiring alterations were made during a safety recall, we did not perform the repair on the terminal. The customer and dealer were contacted and informed of what we found, and the vehicle was towed back to the dealership for repair. The customer was also advised of the problem with the brake switch input being the cause for having difficulty shifting out of park.

2005 Chevrolet Aveo

The next example is a 2005 Chevy Aveo with a 1.6L (L91) 4-cylinder engine and 89K miles. I was asked by the tech to look at this vehicle before he proceeded with any further diagnostics. The vehicle was brought to us for an intermittent misfire that was especially noticeable on acceleration. The original tech performed a scan for codes and a P0302 Misfire Cylinder 2 and P0303 Misfire Cylinder 3 were in history. While loading the engine on a test drive the misfire was evident. As part of his visual inspection he removed the spark plugs and noticed that they were worn out and in desperate need of replacement, so new ones were installed as a starting point however the misfire still persisted while driving. So with the scan tool attached during the test drive watching misfires, he noticed that both cylinders 2 and 3 were still the ones showing a misfire. Since coils are a very common ignition system failure component, especially under load it was the next logical assumption. Normally he would have swapped coils if this was a COP (Coil on Plug) system, but since this vehicle utilizes a 1-piece dual coil pack for all 4 cylinders, this technique would not help on this vehicle. This is a waste spark system that uses 1 coil for a pair of cylinders and fires both the event cylinder, that is on its compression stroke as well as its companion cylinder also known as the waste cylinder, which is on its exhaust stroke. Most of the voltage in this series circuit is used by the cylinder firing the plug on the compression stroke due to the higher pressure in that cylinder. The waste spark cylinder has a less resistance due to the lower cylinder pressure of the exhaust stroke.

Due to the seat of the pants feel we develop as techs, an ignition misfire has a characteristic feel that hints to us it is spark related. Going by his gut instinct, the spark plugs wires were the only option left that could cause this type of misfire. A new set of spark plug wires were ordered and installed. Confident that this would repair the concern the vehicle was test driven once again but much to his disappointment, the same symptoms remained.

So at this point is where I get asked to assist with the diagnosis. A visual under the hood shows everything was installed properly and the spark plug cables were routed correctly. I attached the scan tool to monitor misfires and go for a test drive, sure enough, under a moderate to hard acceleration the misfire occurs only on cylinders 2 and 3 along with a large jerk from worn out engine and transmission mounts.

As I pull back into the shop I was immediately asked by the tech if I thought it was ignition related? It did feel like an ignition misfire but I really needed to dig a little deeper before I could be absolutely sure. I pulled up a wiring diagram of the ignition system and then started to get my oscilloscope out. I think that most good diagnostic techs have a set routine they perform to isolate problems when diagnosing vehicles and by sticking to that regiment they cannot only prove what is not working correctly but also, and just as important, what is working correctly.

I like to try to find some commonality when I see multiple trouble codes to see if a single problem can be causing all of them. Looking at the wiring diagram for the ignition system I find that both cylinders that are misfiring also happen to be on the same coil of the dual coil assembly. The ignition coil module has a 3-wire connector with Pin B receiving voltage in Run and Start through the 15 amp DIS/Injector Fuse.  Pin A is Ignition Coil 2 and 3 Control while Pin C is Ignition Coil 1 and 4 Control. The Powertrain Control Module (PCM) controls the dwell of both Ignition Control circuits. Even though the ignition coil assembly is new it is the one item that both misfiring cylinders have in common. So with the scope attached to the ignition coil I go for a test drive and record my findings.

The blue trace shows the ignition control circuit for the non-misfiring cylinders (1 and 4) while the red trace shows the ignition control circuit for misfiring cylinders (2 and 3).

A close up look at the drop outs in the ignition control circuit for the misfiring cylinders.

Without even needing to pull out of the parking lot I get enough misfires to determine if I am headed in the right direction. Sure enough I notice something occurring on the voltage trace of Pin A of the Ignition Control Module signal which is the Ignition Control for cylinders 2 and 3. The pattern has a lot of drop outs and while the voltage signal for Pin C which controls the ignition timing for cylinders 1 and 4 looks normal. Now I can narrow it down to something in the Ignition Control circuit that is causing the signal to drop out. The downward saw tooth pattern noticed during the signal drop is caused by an intermittent open in the ignition control signal.

When attempting to perform a pin drag test at the connector for the ignition module, the terminal pushed out of the back side of the connector.

With the vehicle in the bay I performed a wiggle test on the harness to try and duplicate the loaded driving conditions and found that when moving the section near the connector of the ignition coil module the engine misfired heavily. Inspection of the harness revealed no breaks in the wiring but when removing the connector of the ignition coil module and attempting to perform a pin drag test on the Pin A for cylinders 2 and 3, the wire pushed out of the connector.

This is how loosely the terminal fit onto the mating male pin at the TIPM. A correctly fitting terminal will not wiggle and exhibit a drag when sliding on mating pin.

The locking tab of the terminal was bent as to allow it to slip out of the connector. I’m not sure if someone tried to remove the terminal at one time or as noted earlier, the powertrain mounts were broken and allowing the engine to jump when loaded which may have caused damage to the locking tab. When the engine moved and the harness flexed, it allowed the terminal to have a poor connection with the mating male terminal and lose signal causing misfires for the corresponding cylinders. When the harness was relaxed during idle and cruise conditions, the connection was good enough that no misfires occurred.

The locking tang of the terminal was bent and flattened allowing it to back out of the connector causing an intermittent circuit problem.

Repairing the locking tab of terminal fixed the misfiring concern, but the customer declined replacing the powertrain mounts even knowing what that it could lead to repeat failures of the harness and its connectors.

Finding either of these failures without the use of a scope would have been a much more lengthy and involved process, especially with the number of circuits on a modern vehicle. By narrowing down a fault to a particular circuit, the diagnosis can be performed more efficiently without unnecessarily replacing components.

Article Details

Thu, 11/01/2018 (All day)

Michael Miller

<p>The intermittent nature of terminal connection problems make them extremely hard to diagnose since they often occur so fast and also so randomly. One technique is use an oscilloscope to help pick out quick glitches in a circuit that would be hard to locate with other testing methods.</p>

<p>terminal connections, auto repair, electrical, diagnostics, intermittent fault</p>

One local service manager of a GM dealer told me that he has seen multiple technician applicants who managed to fiddle around with a small block Chevy in their backyard until they finally got it to start, and believed that one wrench-and-steel conquest and a couple of brake pad swaps on friends’ cars qualified them for an A-tech slot in the dealer service bay. He doesn’t hire them.

By far, we all know the best skill gained comes from performing lots of real repairs on vehicles people will be driving, day after day, one after another. And no matter how many vehicles we troubleshoot and repair, we’re going to encounter some that we will remember for many a year. For me, well, I can think of dozens. But in those moments when we think we know what to expect when we draw a work order but get blindsided, it’s downright annoying.

These are nice rides, but this one wouldn't move.

And then it gets personal – you against the machine – usually one-on-one, slugging it out, sometimes over several days. That kind of meat grinder works well for any skill level from my automotive students to full-blown techs. We never stop learning, and the tough ones put iron in our souls. And for those who are just getting started in this business or are reading these words as a consumer, this, ladies and gentlemen, is what we do.

The Durango

This one came in with a simple “Check Engine” light. And the initial annoyance was that this Durango started out by refusing to talk to us on the enhanced line, and while we did agree to have a look at the MIL issue, we aren’t doing network/comm stuff this semester, so I had my guys back out of the enhanced screen on and dive into the generic OBDII side – which is always a good idea anyway, because what doesn’t show up in the enhanced room might appear in the generic one.

And on the generic comm line we found a P0520 code – that familiar Chrysler oil pressure sensor circuit failure. That’s the one the PCM monitors even if the cluster doesn’t have a gauge. We’ve done these on the V8 Chargers – a few of them, anyway – and so I told the owner of the vehicle we could handle it – no problem. And we did. But we were surprisingly annoyed at just how involved that job turned out to be. And there were pitfalls.

This one was a 3.6L, and the upper and lower intakes had to be removed to access the rear of the oil cooler, where two different sensors are nestled. We packed the intake ports full of rags on the heads at this point for obvious reasons while the sensor swap was under way.

The oil temperature sensor was directly above the oil pressure sensor and also directly in the way, so it had to be disconnected and removed, and then the oil pressure sensor connector had to be disconnected, which turned out to be aggravating because the connector trigger was facing down and inaccessible. So, we’d need to turn the sensor to access the connector trigger. Piece of cake, right? Well, a thick, heat-stiffened wire harness was passing right next to the sensor and that harness was unyielding. Remember, we couldn’t disconnect the sensor wire connector, so a socket was a no-go. And a one and a sixteenth wrench is nice and beefy for turning big, tight fasteners but it doesn’t fit in a tight spot worth a toot. This sensor wasn’t all that tight (1/8 pipe thread), but it was tight enough that even if you managed to shove the open end onto the sensor flats, we couldn’t turn the sensor even a little without that heat-tempered 1.5-inch-thick wire harness forcing the fat wrench off the sensor flats. This was an annoying surprise.
 

I did some bench grinder work on one side of an old chopped-up 1-1/16 wrench I had already modified for something else, and we used that modified wrench to work the sensor around, getting it indexed so we could finger the trigger and remove the connector. We continued to use that same wrench to worry the sensor out, because even with the connector disconnected the harness prevented the use of the sensor socket. We finger-started the new sensor and worried it back in until it was good and tight, then we reinstalled the previously removed oil temp sensor and reconnected all the wires. Then we went back together with it using new intake gaskets and whatnot.

The job was a victory, but it took a couple of dedicated students just about an entire day to make it happen. That surprisingly annoying task was behind us, and so was the Durango and its MIL light.

The 2005 S10

This 4-cylinder S10 was a beat-up little farm truck that came to us with the owner complaining of a hesitation, and sure enough it stumbled on takeoff. But even after acceleration this dog was anemic at best. We applied the fuel pressure gauge to determine that the pressure was always steady and strong. We got a P0300 code, and on the scan tool misfire screen, cylinders 1 and 4 had recorded LOTS of misfires – thousands of them. Initially, I’d have believed there was a coil pack issue, since coil packs fire companions and 1 and 4 share the same coil on those. But this one is fitted with COP coils. What else could cause multiple misfires on companion cylinders? Was the valve timing skewed?

This misfire counter led us in the wrong direction on the S10 – at the end of the day, the farmer drove it home with the MAF connector swinging free. The truck ran good enough to chase cows that way.

Just for grins I had the students check compression, and they found that the firing cylinders actually had less compression (175 psi) than the ones that were reporting misfires (210). The two rear spark plug wells were awash with oil, so we did the valve cover while we were there. Those higher compression readings might have been due to surface quenching from unburned fuel, but it was strange, and we couldn’t see a lot of difference in the spark plugs on the misfiring cylinders and the plugs on the ones that weren’t reporting misfires. Just to be sure there wasn’t a cam/crank issue, we PICO scoped the cam and crank traces to check for a timing situation, but everything lined up perfectly so we moved on.

After the valve cover gasket was in place, we tossed a couple of coils in the reportedly misfiring holes along with a full set of plugs, but nothing changed – misfires were still being recorded on 1 and 4, but it honestly didn’t feel like it was misfiring – it only seemed sluggish and a holding a rag in hand by the exhaust didn’t show any puffing. And the ACE Misfire Detective was confusing enough as to be no help at all on this one.

At this point, I decided to focus on the MAF sensor, because, according to my professional eye, the airflow readings didn’t seem to reflect reality, even when MAF was the only PID being traced. Interestingly, when we unplugged the MAF and did a test drive, the truck ran like brand new, and as I peered through the sensor with my streamlight the hot and cold wires seemed dirty – but cleaning the sensor only helped a little. This one needed a new MAF, but when we showed the farmer how good it ran with the sensor disconnected, he opted to drive it that way and ignore the MIL, since most of the time he’s using this truck to herd cows. His call, I guess. But the surprisingly annoying part of this job was that the misfire counter pointed us in the wrong direction initially.

The Edge

One of my colleagues drives a Ford Edge – awhile back we had to replace the brake booster (which was dreadfully annoying). Speaking of brake boosters, for a short side story (annoying) we had to replace the booster on a 1998 F150, and after we changed the booster, the brake lights were always on because the booster pushrod had some flashing on it that had to be ground off so it wouldn’t keep the switch closed all the time – didn’t see that coming!
 

This stoplight switch on the 98 F-150 wasn’t giving a problem until we replaced the booster – I ground some flashing off the molded-and-cast booster pushrod on the rebuilt booster to fix this one

On the Edge this time around she was having issues with her A/C. She reported that it’d run for about 30 minutes and then get hot on one side (dual zone), so, after we duplicated that and saw erroneous readings coming from the blend door actuator on the driver side, we replaced that actuator with a Dorman unit and let her try that, but after a few days, the Edge returned with the complaint that the A/C that would totally stop cooling after about 30 miles of driving.

In addition to that issue, her radio would always begin to search wildly for no reason after a few minutes – obviously an APIM problem (the 2012s are problematic this way), which we figured might have something to do with the A/C issue, but it didn’t. We did that wacky Ford PTS software update/reflash with the IDS (with some guidance from Joey Henrich’s AE tools guy), but the APIM radio function still wasn’t fixed, so on her orders, we ordered a rebuilt replacement APIM from Ford. The core charge is $500 on one of those, by the way, and replacing that unit fixed the radio – but by the time the APIM came in, we had already figured out the A/C problem.

These were the readings we got on the Edge after it stopped cooling (with the A/C running, no less). After the expansion valve was replaced it was good to go with limitless cold air.

After letting the A/C run in the service bay with the recycler connected so we could watch the pressures, we noticed that when the register got warm, the low side had drifted into the negative and the high side was hung at just over 150 psi – much lower than it had been when the A/C was cooling. That was our smoking gun.

An expansion valve took care of that one. As an aside, the owner had, on a previous day dropped by a dealer shop when she was in another town for a quick check of the A/C and they told her she’d need a $1500 evaporator case replacement to take care of the no-cooling issue because, in their words, “the actuators aren’t communicating.”  I’m not sure what pocket to put that in, but she was glad she had opted against letting them do that!

Mysterious bearings

Another one of my colleagues drives an old Sentra that had developed a nasty noise, and after we determined by doing some tire-swapping that it was a bearing noise, we went out of our way to make sure we got the right bearing – these can be really tricky sometimes (can I get a witness?), and this one was no exception. I told the owner that we might wind up having to replace both bearings and he gave us his blessing. Using the Chassis Ear® we thought we had it pinpointed as the one on the left front, (swerving seemed to point to that bearing too), but when we broke it down I could have a good look at those shiny balls and race, I could tell that we had misfired on that – Mr. Murphy is alive and well, you see. But we were at the point of no return, so we installed that bearing and drove it again – no change.

The only difference between the noisy bearing and the non-noisy one was the color of the grease – there was no visible wear on the balls or the race.

With that, we attacked the other bearing, which still didn’t show any brinelling or wear as we had supposed, but we did notice that the grease in that bearing was discolored – instead of a healthy cream color it was kind of brown, and even though the balls and races looked good, replacing that bearing eliminated the noise. We had no smoking gun, but we had a solid fix.  That always bugs me, because I like visual verification of that kind of thing. Granted, you don’t always get that with transmission or ring and pinion gears, but with bearings you usually see something. This time, not so much.

The Altima – A perfect storm

This one came to us with the story that a guy at a shop in another town had replaced the transaxle, but that after only two hours of driving around, the transaxle had started slipping and then stopped pulling and now the guy who had changed the transaxle was telling them it needed a flywheel. So they brought the car to us with a used flywheel they wanted installed. How tough or annoying could this one be?

This bushing was never intended to contain a spinning torque converter snout – subsequently, when the flywheel failed while driving, that’s exactly what it did for probably 2 hours – and the results are plain to see.

This flywheel failed in such a way that the engine was able to spin the bolt circle very nicely – this was the perfect storm for the torque converter and its bushing, since the flywheel was stationary all this time – as was the converter

We worried that CVT out of there to find that, although we had unbolted the torque converter, it stayed attached to the engine when the CVT was removed. Furthermore, it didn’t want to come off – at all. But it was rattling around loose. After using a big prybar and a hammer and whatever else it took, I managed to get the torque converter on the floor.  It was at that point that I discovered a very serious issue.

The flywheel had broken smoothly enough that the engine was spinning the now-separate center of it. The outside of the flywheel and the torque converter were both sitting still while the engine was spinning to beat the band, and the pilot bushing those Nissans have in the back of the crankshaft had been whirling on the pilot of that converter until the pilot had become red hot and had swelled to the point that the pilot bushing came out of the crankshaft when we pried the converter out of there. This was surprisingly annoying, and that wasn’t all.

On the left is a good bushing in place (this was the 2004 engine). On the right is the cavity the destroyed bushing came out of when the flywheel was pried off. Note the cracked and overheated flywheel.

This was ultra-nasty, because all the information I found was that the bushing in question is not obtainable apart from buying a replacement crankshaft. Granted, with the right dimensions, a machine shop could have made us one on a lathe, but machine shops are hard to find these days.

As it was, this customer got lucky. It just so happened that I had a defunct 2004 Altima powerplant sitting in the engine shop that had been swapped out because it was knocking, and I got the bushing out of that one. It was an annoying process, but with a high-speed cutter, we made it happen. The bushing was a perfect fit, and with a replacement torque converter and the CVT back in place, the Altima was good to go.

Far left is the bushing in its boss – we used a high-speed cutter to surgically remove it. Middle is the bushing – far right is the bushing being driven into the rear of the crank on the Altima.

The customer asked if the previous tech had done anything wrong to cause this. My answer was that he hadn’t, and that was that.  I told them about a transmission we had replaced in a four-wheel drive Expedition that came back a month later with a busted flywheel it’s always annoying but sometimes it happens.

Article Details

Sat, 12/01/2018 (All day)

Richard McCuistian

<p>We never stop learning, and the tough ones put iron in our souls. And for those who are just getting started in this business or are reading these words as a consumer, this, ladies and gentlemen, is what we do.</p>

<p>auto repair, pattern failures, bushing, flywheel, Richard McCuistian</p>

We usually do our best and most efficient work on vehicles with which we’re familiar, but there are times when even the ones we know the best can smack us around – particularly if we make the wrong choices. But in the midst of troubleshooting and repair, we usually learn the most from our errors. An old cowboy proverb I read years ago can be paraphrased by the statement that we usually learn good judgment after having experienced the negative results of bad judgment. In the world of automotive electronics, that good judgment learning curve can be deep and steep, even if we’ve already fixed a multitude of vehicles, and I’ve been in this business for more than 40 years now.

The F-150 and the not-so-perfect storm

A 2003 four-wheel drive F-150 5.4L with 213,654 miles was one of those bad-judgment learning curves. Sometimes trying to save a customer some money costs us a heck of a lot of work. This was a windshield wiper concern. How hard could it be? Somebody had already replaced the multi-function switch, too.

This 2003 F150 is in pretty good shape, but you don’t need to drive in the rain without wipers and so here it is.

For the last 20-plus years on these F-150s, the wiper system has its switch (part of the multifunction switch) wired to a dedicated control circuit in the Generic Electronic Module (GEM), and three relays in the underhood fuse box; one for low speed, one for high speed and a third relay for the washer motor. The algorithms in the GEM module software are supposed provide the relays with their marching orders based on the chosen switch position.

The wiper switch portion of the GEM module’s IDS datastream screen is a long tracking bar that has failure areas on each end and normal switch positions in the middle. As we cycled the switch through its positions, the IDS put shadow tracks in all the right places and none of the wrong ones, indicating that the GEM was reading crisp, accurate commands. So far, so good, but still no wipers.

When this first wiper module didn’t work right (top), I had the salvage yard snag me another module – which turned out to be a problem because Hurricane Michael heavily damaged the yard’s Panama City warehouse and replacement module was still on the truck inside the warehouse.

I was able to turn the wipers on by telling the IDS to activate the wiper relay, and when I then activated the speed relay, the wipers would go into high gear. When I turned the wiper relay off, the wipers would park. I could select the washer pump relay and the pump would wet the windshield with its spray.

Removing the steering column shrouds, we found the square connector crumbling, so we bought a replacement pigtail and put it in place with solder and heat shrink to no avail – the wipers still didn’t work. As an experiment, we had the parts store send a new switch, because these switches look exactly alike from year to year but are different internally – I found that out the hard way when I was at the dealer. From previous experience I discovered that a ’98 switch won’t work on a ’99 model, and so on. You must use the right switch. Period. The new switch changed nothing, so we sent it back.

So why wouldn’t the GEM activate the relays when commanded by the switch if the IDS indicated that it was receiving (and reporting) the switch commands? This had to be a problem within the GEM module, and I usually get black boxes from the salvage yard when I can, sometimes because replacement modules aren’t available at the dealer and sometimes because the replacements are so expensive. So, I gave the salvage yard the number that was on the old module’s sticker and bought a $65 used module that was supposed be the right one. The sticker on the replacement did say it was for a 4-wheel drive F-150, but it didn’t have the same prefix and suffix numbers as the original module.

We used the IDS “Programmable Module Installation” feature to save the existing module’s data in the Toughbook, and then we installed the replacement module (which rides piggyback on the fuse panel in true Ford style) and did the requisite data dump into it from the IDS. Well, we got an error message. Was this even doable with a used module? I wasn’t sure. We were in discovery mode. With the used replacement module in play, you could turn the wipers on first low and then high and they would work, but when you turned the wipers off, they would remain on high, and sometimes the washer would randomly start spraying.

I had installed new/rebuilt GEM modules like this, but this was the first time I have ever tried to install a used GEM module like this. Was it a bad idea? It was beginning to look that way.

At this juncture it was evident that this module obviously wasn’t going to work for us on this job, but it did let us know we were moving in the right direction. The salvage yard said that there was another module at their warehouse that did have the right prefix and suffix numbers, but we ran into a hiatus on that one because Michael the hurricane washed that warehouse away the next day, so we had to wait for the next GEM module. But when it arrived and we did the Programmable Module Installation again, we got a different error message and different errors. This time, the wipers worked almost perfectly but the power windows didn’t because the GEM module wouldn’t turn on the accessory delay relay. We had wipers but no windows. We So we were back to square one. The discovery was that, in this case, it would have been smarter to begin with a refurbished module from the Ford dealer.          

A ’96 Jeep Grand Cherokee

This Jeep wasn’t a discovery and judgment case, but it bears mention. It came to us with a non-functional A/C system and no compressor operation. This was The Neutronics identifier showed us nothing but air in the system, and so we ran a 15-minute vacuum, didn’t see appreciable vacuum decay, and went on to shove the requisite amount of cold stuff into the piping. The A/C worked at this point, but we knew there was a leak somewhere, else it wouldn’t have been empty to start with.
 

Now that we knew the compressor and the electrical part of the A/C were operable, we pulled the cold stuff back out and used 150 psi of dry nitrogen to see if we could find a leak that way. We didn’t. So we did another vacuum, injected some dye, and recharged the system. We let it run for a bit and then shut it down to black light it for leaks, but we didn’t find any under the hood. It was time to look deeper.

This considerable dye drip led us to the leaky evaporator, and while we were there, at the customer’s request we replaced the heater core as well. The orifice tube was in dreadful shape; it took the whole pipe to get this one, but I wanted eyes on the original – it was a good call for sure.

Starting the engine, we put the A/C on again and waited a bit until the evaporator started dripping, and that’s when we saw dye — a LOT of it — in the evaporator drain. Apparently, it would hold vacuum but not pressure. The customer opted for a new heater core and evaporator and we swapped both in-dash heat exchangers out, along with the liquid line, which has the orifice built in. I cut the orifice out of the old line and found that replacing it was a good move. This was the first one of these Tim had done, but he made it happen, and the Jeep has good cold air.

A 2008 Charger

This black Charger turned out to be another electronics adventure and an exercise in discovery and judgment. The complaint was that you had to attempt to start it about 100 times before it’d finally wake up and fire up; that’s the way the owner described it and that’s how I wrote it up and he somehow got it started and brought it the next morning.

Since the scan tool wouldn’t talk and the CAN bus was dead, we poked around in the schematics and determined that the Totally Integrated Power Module (TIPM) might be at fault – interestingly, the owner came up with a used one he got from somewhere and we popped it on there to no avail. Nothing changed at all.

ALLDATA Tech Assist suggested that the Wireless Ignition Node (WIN) might be at fault and said we should check power and ground at that funky little box — this is what most people might call the ignition switch, but it’s a CAN module and apparently wakes up the bus and the other modules, which it was refusing to do. It had power and ground, so we found a rebuilder in San Antonio who would refurbish it for $149 if we’d send the WIN and both fobs, so we did. When the node came back, the Dodge fired right up, but there were other issues — the door locks wouldn’t work unless the WIN (the key) was turned on. With the key on, the lock buttons and the fobs worked fine. Also, the accessory delay problem wasn’t working right – the windows and the radio always kept working even after the door was opened. Oh, and the courtesy lights wouldn’t work unless the key was on. Could the WIN be causing this? For some reason it had no idea the doors were open, and the cluster seems to be the module receiving those inputs.

What surprised us was that fuse 14 was missing, and although fuse 17 also feeds battery power to the cluster, 14 feeds an important part of the cluster as well – and the absence of that feed caused all manner of confusion. Somebody removed that fuse before we ever even saw the car. And that didn’t help either.

As a hail Mary pass, we ran through a check of all the fuses and found fuse 14 missing from the rear PDC (by the battery in the trunk). At that moment we didn’t know it, but when we researched, we found that Fuses 14 and 17 both feed the cluster, and when we installed the requisite 10-amp fuse in position 14 the Dodge was good to go – locks, retained accessory power, courtesy lights, everything. Somebody had planted this bug before we ever saw the car.

A 2008 Nissan Quest

This was another inoperative A/C – we had shoved some juice into this one for the first time in its life about four years ago and it had worked well until about halfway through this past summer. I threw the job at one of my folks who needed to get some A/C troubleshooting worksheets done, and I got involved after she did her preliminary diagnosis.

The Quest owner didn’t report engine overheating, only A/C system failure, and that’s how this one started out.

The Neutronics box had sniffed the juice and given a green light — 100 percent 134a, and when we connected the refrigerant recycler we found we had nearly 100 psi of static pressure, but when we fired up the engine and turned the A/C on, the pressures started climbing and kept going up. The high side went above 400 pounds within 2 minutes and inside, the cooling went away. We noticed that one of the two condenser/radiator fans was running slow and the other one wasn’t running at all, so we shut everything down and did a quick fan electrical test.

This is a fan test I’ve mentioned before, and there are two solid benefits.  First, if the fan fails this test, it’s bad every time. Second, this test can find an extremely intermittent fan problem, and often does, if just one or two of the commutator strips is bad. I devised this method when I was at the Ford dealer and we were having a lot of hard-to-duplicate intermittent fan failures.

There are several ways engineers have wired two-speed fans, and this one seems to be unique to Nissan. These Nissan fans have proprietary relays with two sets of contacts and each fan has four terminals, two of them grounds, and two of them powers for controlling cooling fan speeds and so in order to do our test-light continuity test, we disconnected the condenser/cooling fan that wasn’t running and connected a jumper to one of the two ground terminals in the fan connector (NOT the harness). The other jumper was connected in series with a test light to any positive battery terminal on the motor, and as we turned the fan by hand, the light was winking off more than it was on. That’s a go-no-go fan test that’s always reliable. That one got a replacement fan and a draw-down and recharge with the right refrigerant charge and was once again a comfy ride.

The high side pressure was alarmingly high before the fans were replaced – on a different Nissan, a pickup – we found a bad belt-driven fan clutch causing a similar problem, but it would slip the A/C belt after a few minutes of A/C operation.

The SRXs

This family has two Caddy SRX rides, a 2005 and a 2008. The 2005 came awhile back needing front shocks (the front would bounce up and down for about seven seconds on a sudden stop) and with transmission concerns — erratic shifting, and when we checked the transmission oil it looked like brake fluid, dark and strange — so we did a full fluid exchange, then followed up by yanking the pan, replacing the filter, and adding the necessary quarts for that, and those shifting problems were gone. We also popped a set of front struts on there to handle that bouncing issue.

This was the leaky lower radiator hose we discovered while investigating the high-pressure cutout switch on the Cadillac. I’ve seen more of these clamps breaking this way over the past couple of years than in the previous twenty combined.

The 2008 SRX belongs to the parents of the lady who drives the 2005 model, and she showed me a nasty clunking noise under the front end while driving around the parking lot and over small bumps as well as an inoperative A/C concern.

This steering rack leak and the pricey high-pressure cutout switch, when added together, drove the estimate high enough that the owners decided it was time to trade the Cadillac in and let somebody else deal with the problems.

We didn’t see anything that was loose or needed replacing on the front end, but we did apply some heavy torque to the control arm bolts (we got a full turn on each bolt) and the clunking was gone.

As for the A/C problem, the registers were almost always hot, but sometimes they’d be nice and cool. There was plenty of good clean juice in the pipes, but no compressor operation, and our testing (scan tools and schematics) led us to the high-pressure transducer, which is very pricey and mounted just inboard of the driver’s front wheel well.

Well, while we were there, we also noticed a leaking lower radiator hose due to a rusty and cracked spring clamp (this one lives up north with the salt) and we also discovered a nasty power steering leak at the driver’s end of the steering rack.  When I priced out all the repairs, rather than giving the go-ahead, this lady called her husband and they agreed together that this vehicle needed to belong to somebody else; she decided her folks needed to trade it in without making any repairs, but we did replace that broken spring clamp with a nice stainless-steel Gates screw clamp. All in all, it was a good day, I guess. 

Article Details

Tue, 01/01/2019 (All day)

Richard McCuistian

<p>We usually do our best and most efficient work on vehicles with which we&rsquo;re familiar, but there are times when even the ones we know the best can smack us around &ndash; particularly if we make the wrong choices.</p>

<p>auto repair, diagnostics, Motor Age, Richard McCuistian</p>

When I was at the Ford place, I drew a work order for a charging system fault on an old F-150 and told the customer she needed a new alternator – and she went and bought one from a local parts store – well, that one wound up being bad, so I yanked it off and she took it back, had it checked on their machine, and brought me another one. This happened four times – we finally got a good one, but she was kind of ill that she had to pay us to replace the alternator four times – thinking she’d save money buying her own part, she made a series of bad choices. Had those bad alternators come from our parts room, the Ford Authorized Manufacturer would have paid all that labor.

With these funky big tires contacting the splash shields during turns of more than about 15 degrees, this one is no fun to drive — but it wasn’t written up for that.

On a slightly different note, I used to hang out when I was off work at Sambos drinking coffee back in the late ‘70s with some of the locals in Port Arthur, Texas, and when I overheard one of the patrons asking a young waitress about her car, she told them she had a ’63 Buick Special but that the “motor had burned up” and she couldn’t drive it. I chimed in to ask if she had run it out of coolant or oil, and she told me it had caught fire under the hood while she was driving and had been sitting in her parents’ driveway for months.

She went on to say that they had given her a coil, a distributor cap and some wires for her birthday, but nobody they knew wanted to attempt the fix and they couldn’t afford to hire a shop to do it. I asked if I could take a look, and she agreed, so I dropped by her parents’ house and opened the hood on that little V6 to find that the engine fire had been wall to wall – the wire harness was little more than a bunch of bare wires, and the ignition components were, as expected, nothing but crust and ash. I wondered if I had bitten off more than I could chew; I couldn’t even tell where the fire had started or why, but I dove in headfirst. 

Retrieving some rolls of wire I carried in my truck toolbox, I carefully unplugged the mostly melted wire harness from its various connection points and using cheap butt connectors and electrical tape (I wasn’t going to spend the time it’d take to solder and heat shrink everything), I rebuilt that underhood harness one wire at a time on the tailgate of my pickup, then plugged it all back in and installed her new distributor cap, wires and coil. I hooked up my jumper cables, we spun it over, and it fired right up and ran like a champ. The whole job only took a couple of hours, so I charged her $25, and she paid me with multiple rolls of coins from her tip money.

The Commander

A friend of mine brought his son’s 2006 Jeep Commander, 4.7L V8 with a 5-45RFE transmission and 187,854 miles on the odometer, telling me he believed water was making its way into the #8 cylinder, because the vehicle had overheated a few times and now it was misfiring on that one. We found his misfire on the cylinder he indicated, but a quick look at all the plugs didn’t show any evidence of coolant ingestion at all, only a sooty plug on the dead hole. So, my man Charles tossed a set of plugs in there, and in the process of our testing we discovered the compression was low on that cylinder. Further, Charles said that with it idling he was hearing something under the valve cover he didn’t like, and to get the valve cover off, he had to recover the refrigerant.

Any shop who doesn’t use a refrigerant identifier does so at their own peril. Without one, this kind of contamination gets spread from the recycler to other vehicles like a disease.

When we did the refrigerant I.D. with the Peter Coll Neutronics tester (a shop should always do that!), we got a big fat red FAIL light – 5 percent hydrocarbons in there, possibly from some fly-by-night canned stuff. We had to use our dedicated tank and machine to suck that garbage juice out. When Charles got the valve cover off (no fun), he found the rearmost roller rocker out of place and lying fallow on the head. How did this happen? Somebody else might know, but I don’t. We removed and collapsed the lifter so we could get the rocker back in without too much trouble, and that took care of the engine skip, but we weren’t finished – not by a long shot. More about that one in a minute.

The Buick

One of our staff drives a 2007 Buick Lucerne that was purchased from the local GM dealer as a very clean used vehicle, and it’s outfitted with that tried-and-true 3.8L V6 GM used for so many years. It had been sporting an MIL light for awhile along with a P0420 code, but the director in charge of our vehicles said the catalyst had already been replaced with an aftermarket unit before the car was purchased and he wasn’t concerned about that. What did turn out to be a concern after a few thousand miles was that the Buick died and came in on the hook with no fuel pressure.

The Director’s 2001 Toyota Tacoma hunting truck died when he was leaving his driveway that morning, and we initially diagnosed a bad fuel pump and then found this. He hasn’t owned the truck for very long – and this was done before he bought it.

It was interesting that about this same time, the 2001 Tacoma driven by the director died from a lack of fuel pressure as well. We ordered a Delphi fuel pump from the local parts supplier for the Buick and initially ordered a fuel pump for the Tacoma, but after we got the Toyota pump out, we found somebody had already replaced it (just the pump, not the whole thing) and did a crappy job on the in-tank wiring patch, so we got rid of the butt connectors, fixed the wiring the right way and sent the pump we had ordered back to the parts store to get the Tacoma done.

The good trace (top) shows when the Buick started and ran the way it was supposed to. The bad trace (note the down spikes at the top when the starter was operated) shows that spark and fuel pulse were initially absent on the long spin

One of my people rolled into the trunk on that Buick with an air ratchet and a fan blowing the fumes away and replaced the pump module with a new Delphi unit, but then about six weeks later, the pump died again, and this time, since we were between terms and I was off work, the Buick wound up at the GM dealer where it had originally been purchased – and the director called my cell phone to say that the dealer said the pump was bad.  I called and explained to them that the pump was a Delphi pump, but they said since they didn’t sell that one to us, they’d need us to get a replacement pump from the parts store – which I did, and they installed that one – it was back on the road.

Well, the odd thing that happened next was that when the car was started after a hot soak it’d immediately die and would need to be re-started, and we found the second new fuel pump failing to hold rail pressure after the vehicle was shut down. A third replacement Delphi pump held rail pressure at shutdown, but sometimes the car would still pull that odd start-and-die stunt. This was getting interesting. Further, there were a couple of times when the car would either lose power or just quit while driving and fail to re-start, but we could never duplicate this. We DID, however, get it to start, die, and then spin about 10 seconds before starting, and we got it to repeat this somewhat regularly, if not every time. And while it had nothing to do with this start-die problem, we obtained a Walker bolt-on replacement cat to get rid of that annoying P0420 once and for all. And it did.

For the other issue, I broke out the Waekon Industries Flight Recorder® (WAE-45364), which is kind of pricey, but records ignition, fuel injector pulse, battery power, and one Auxiliary data plot of your choosing in an internal buffer when you tap the record button, and the graphs can be retrieved on your PC with the dedicated software.
 

We had successfully fixed a Chrysler Crossfire that had stumped the Chrysler dealer using this same tool (see “Methods, mysteries and frustration,” May 2013), so we used the tool on the Buick and found that, when the concern was duplicated with the auxiliary measuring power to the injectors, there was indeed power to the injectors. However, the spark and pulse weren’t consistent during the extended spin. After replacing the crank and cam sensors to no avail, we replaced the underhood fuse box because it has a gaggle of those integrated relays that can’t be replaced — one of them being the run/crank relay; if that relay doesn’t deliver power (or not enough power) to the PCM, we reasoned that it might cause this concern. It was a Hail Mary pass, but at the time of this writing, about six weeks has gone by with no further complaints.

The 2007 Silverado and the Fusion lug

This truck came in for a routine service and an oil leak, and when we applied the dye and the black light, we found the oil oozing out around the oil filler cap – which was peculiar, but not unheard of, particularly on these GM V8 truck engines that have the PCV system integrated into the driver side valve cover. The students who did the service also reported moisture in the crankcase, another indication of the PCV issue. We replaced the valve cover and those concerns evaporated.

At first, we put dye in the crankcase, then we got under the truck and saw the trickles of oil, which we tracked to the filler cap. That, coupled with the moisture in the crankcase, fingered the valve cover, which has the integral PCV. This one got a replacement valve cover.

On a side note, we found a Camry leaking oil from around the oil filler cap too, but it turned out that one just needed an oil filler cap.

We were doing a routine tire rotation on a 2012 Fusion when one of my people came to report that one of the lug nuts was spinning round and round on the left rear and they couldn’t get the tire off. That one was because of a nut that was initially cross-threaded and impact-forced right at its tip. This wasn’t the first one of these I had seen – we had an Altima with the same issue awhile back, and it was a bear. The folks who use an impact wrench with no torque stick tend to think that too tight is better than just right, and after a little of that, the threads begin to gall and sometimes the nut just won’t move. If the splines on the stud are sufficiently strong, the stud will break off. If not, they spin in the hub, like this one did, which becomes something of a problem.

I’ve seen this more than once — this lug nut was crossed up by somebody on the starting threads and then they tried to force it with an impact wrench, which effectively welded the lug nut to the stud. In other cases, the impact wrench distorts and galls the threads all the way down due to overtorqueing. Oil drain plugs are prone to a similar kind of failure.

I used a two-pound hammer to drive an old MAC prybar in between the wheel and the hub with enough force so that we were able to foul the head of the lug stud and get the nut off, and then we replaced the stud and the nut. At my shop I teach them to spin the lugs on there with the impact on its lowest setting and then follow up with a torque wrench. Then I place the students in shops where all that careful torqueing (and even the practice of wearing safety glasses) goes out the window and they wonder why I even taught them that to begin with. Oh, well.

Back to the Commander – and a Dodge

In search of the overheating problem, we noticed that there were coolant stains on the exhaust back below the heater core area and we initially thought there might have been a heater core issue, but then, there was no coolant in the passenger side floor. Was this one of those with a secondary drain for a leaking heater core? No, there was a hose issue of some sort going on back there, and initially we found that one of the clamps was loose and dangling, but that wasn’t our leak either. What we found was that somebody had replaced an original heater hose tee with a plastic one that looks like it came from a hardware store – it was a size too small, not made for coolant heat, and was cracked to boot, and the clamps had egg-shaped the plastic. It’s a wonder it was holding coolant as well as it was.

First, we noticed the coolant drain stains, then, above that, the clamp somebody had never tightened. Finally, in a totally different hose, we found the cracked and lousy tee.

We replaced the tee, pressure tested the system, liked the results, and then drained the radiator, which didn’t have much coolant in it. On this one, because the thermostat is in the bottom radiator hose, you drain almost nothing out of the engine block unless you yank the ¼ inch pipe plug out of the side of the block to let it gurgle out of there – we did that. Afterward, I wanted a full load of 50/50 in there, and I poured it in through the upper radiator hose with a funnel to fully purge the engine block water jacket of air before we did anything else. Remember, the thermostat is in the lower hose. Toyotas, old VW Rabbits, and some other platforms are built this way. Incidentally, Ford’s 2.8L V6 was configured this way as far back as the ‘70s (think Mustang II).

Okay, so we fired up the Jeep and let it run for a while – there was a Check Engine light, and among some other codes, we got one for a cooling fan issue, and this had been an overheater – so we went back at it.

This is one of those Jeep vehicles that has a belt-driven fan AND an electric fan, and we noticed that somebody had pocketknife-shaved the cooling fan wires in spots, probably trying to see if there was power to the fan. We checked the fan electrically with a test light wired in series but found no open segments. Pulling both fan relays, we found no power at their common terminals, and that’s when we noticed that blown 50-amp fuse that probably happened when somebody was fiddling around with the fan wiring. With the fuse replaced and a smooth re-test, the fan came online and everything was dandy.

I like to dissect the fans that fail – usually the brushes are worn out, but this one (from the Charger) died because of a cold solder joint.

Speaking of Chrysler V8 overheating problems and customer bought parts, we had a 2006 Charger that came to us with a new radiator in the back seat that the owner had purchased online, along with specific instructions that we were to replace the radiator first – in true form, they had a friend of a friend do the troubleshooting and he told them that was what they needed. We followed those instructions (replaced the radiator) but we also did a pressure test, which revealed the actual problem — it had a leaking water pump, so we did that too. But once again, we weren’t done yet. In sewing that job up, we noticed the fan (a dual unit) wouldn’t run, and our test light test of the driver side fan motor revealed an open motor. With a new dual fan, a new water pump, and a new radiator, that ‘06 Charger was cool to go.

Article Details

Fri, 02/01/2019 (All day)

Richard McCuistian

<p>A friend of mine brought his son&rsquo;s 2006 Jeep Commander, 4.7L V8 with a 5-45RFE transmission and 187,854 miles on the odometer, telling me he believed water was making its way into the #8 cylinder, because the vehicle had overheated a few times and now it was misfiring on that one.</p>

<p>auto repair, diagnostics, Motor Age, Richard McCuistian, Buick, Commander</p>

I think we have all been in the situation as a shop owner, mechanic, technician, handy man or whatever you like to be called where we are approached by a family member or a close friend because they know one thing. They know you can “fix things.” Ninety-nine percent of the time we are more than willing to lend a hand, or at least I am, and especially in this case. It was my one and only sister who called me. Mind you all three of her brothers are mechanics as well as her dad and we all own shops but it was my turn this time. Either they copped out or I was just the first one who answered her call.

She called to let me know that the front wipers on her 2014 Dodge Grand Caravan with 71,870 miles on the odometer had stopped working and wondered if I could take a look at it for her. She goes on to tell me she already spoke with dad and one of my brothers who both referred her to me. So there, I got my answer as to where I fall on the call list and was voted the best “family mechanic” for the job, apparently.

That day she swung by the shop and explained, or I suppose the better word would be, hoped it was “just a fuse.” Because we all know fuses are cheap! Knowing the problem that seems to follow Chrysler around since the invention of infamous TIPM, I was pretty sure we were not going to find a “bad fuse.”

Figure 1

I pulled up a diagram (Figure 1) and grabbed a scan tool so I could see wiper inputs into the TIPM. After releasing a few fasteners on the cowl so I could gain access to the wiper motor plug I was ready for some testing. Looking back at the diagram it is a relatively simple lay out. One fuse (that was not blown), two relays and some logic to control it all. I wasn’t too concerned at the moment how the input from the wiper switch made it to the TIPM and how many modules it ran through to get there but I could see on scan data that it did make it there. Every selection on the wiper stalk was being displayed in the live data. The next obvious step was seeing if the power was being sent through the relays and up to the wiper motor. I quickly discovered at this point it was not! The wiper on/off relay appeared to be permanently latched to pin 87a which leads straight to a ground. Knowing all of the inputs were good, the testing was good and 100 percent definitive I gave her the bad news.

It's going to cost HOW much?

We can all assume what happened next when I revealed the cost of the new TIPM plus the cost of the 2-day subscription to Tech Authority so we could program and restore vehicle configuration to finish the repair. I think some call it puppy dog eyes, sob story or crying the blues. In either case I saw this as an opportunity to try and repair the failed relay on the board with nothing to lose. Besides, it was my sister, not a “real customer” right? I told her the risk involved and also exposed the fact I have little to no experience with printed circuit board repair. We agreed on the $15 fix and I ordered a new relay (Figure 2).

Figure 2

Figure 3

What did I get myself into!? The TIPM comes out of the vehicle in about five minutes however I was the better part of 45 minutes trying to get it apart to get to the good stuff (Figure 3). The smart phone came in handy during this part as every fuse and relay had to be removed. There were four stacked circuit boards that were pretty resilient and eventually I was able to get down to the green printed circuit board that had the relays soldered to it (Figure 4). The only down side was there were about six relays on the board and I had no idea which one of the 10 pin double relays was at fault.

Figure 4

Figure 5

Not knowing any better way, I decided to energize the control side of each relay and determine which one did not work. I was later told by several people that this was not a good idea and could have caused some damage. Either way, I was quickly able to determine the one at fault (Figure 5).

Figure 6

Now came the fun part. Trying to de-solder the old relay. I bought some fancy magnifying glasses that helped tremendously, I also bought a solder sucker and some solder wick. I failed miserably at both to say the least. 20 minutes into it I started to wonder how much heat and fiddling one of these boards could take (Figure 6). The answer to that question is a lot! At least it was in my case. Trial and error eventually got the old relay removed from the board. I can say I was relieved to see when I took it apart that the contact was clearly fused together (Figure 7). At the same time, I wondered if this whole mess was going to work once it was put back together.

Figure 7

Finally, the EASY part. Soldering the new 10 pin relay in was a breeze. Rest assured snapping all of the plastic bits together is way easier than taking them all apart. It was a little tedious with sausage shaped fingers full of arthritis to do the job but it was very satisfying to see the finished product (Figure 8).

Figure 8

But will it work?

Now for the moment of truth. I installed the TIPM in the vehicle, cleared the codes, pulled up some data, said a little prayer and turned on the ignition. Palms sweating, I flicked on the wipers and they WORKED! High, low and intermittent. I actually did it! I know too many of you it may not sound like a big accomplishment but honestly it felt good to carry out a repair I would have never thought of doing in the shop for a customer. Sell a TIPM? Sure, we do that on a regular basis. Tear one apart and do a repair? No way! As a shop owner I can’t be married to a vehicle for an experimental repair that could quickly go South. On my sister's car, well that is a different story. My dad always called it government work when we had to work on family’s cars. I never really knew what it meant but it sounded good. In this case it has a happy ending. She had her van fixed on the cheap and I looked like a hero. Although truth be told I think I had a little luck on my side that day.

As a side note I posted this repair on my YouTube channel and reaped some of the many benefits of having one and that benefit is community. I received thousands of comments full of tips and tricks for removing soldered pins as well as the correct types of tools that should have been used. In my opinion that was the biggest benefit I received and continually receive from my channel. There are a lot of folks out there from a lot of different corners of the world willing to share their knowledge and expertise on subjects that are way outside of my wheel house.

Article Details

Fri, 03/01/2019 (All day)

Eric Obrochta

<p>I think we have all been in the situation as a shop owner, mechanic, technician, handy man or whatever you like to be called where we are approached by a family member or a close friend because they know one thing. They know you can &ldquo;fix things.&rdquo;</p>

<p>auto repair, Eric Obrochta, South Main Auto, 2014 Dodge Grand Caravan, diagnostics, family, mechanic</p>

Social media is an amazing thing in my opinion. From a diagnostician’s perspective, having the ability to reach out and communicate (in an instant) with like-minded individuals across the globe, allows for some tremendous opportunities. Each one of us sees through a different perspective, has different experiences with different vehicles and can offer data that we might not encounter otherwise. With a group of like-minded individuals that both share a passion for the automotive industry and a desire to learn/share/educate equally, it’s a winning combination. Its these very traits that helped to make an important and otherwise expensive diagnostic decision, easy as pie.

Same problems, different terminology

Earlier this month, I crossed paths with a fellow tech by the name of Ryan Colley. Ryan works in a shop called Elite Automotive Diagnostics, located in a small village called Bishops Hull, in Taunton, United Kingdom! Ryan reached out to me because both of us network commonly with other techs through a few Facebook automotive groups. Each one of us in the groups has a particular arena that they are comfortable in. I happen to be comfortable analyzing pressure waveforms acquired from different points on the vehicle. This is the reason Ryan reached out to me. Ryan is faced with a 2006 Audi S4, housing a 4.2L DOHC-V8 engine under its hood (or should I say “bonnet?") as seen in Figure 1. The engine performs very poorly and was brought to his workshop for analysis. Ryan quickly recognized the symptoms the vehicle — with 77,564 miles and an automatic transmission — was exhibiting, as the cranking cadence of the engine indicated something mechanical is “going to pot.” The vehicle’s PCM was scanned for DTCs. Looking at the DTCs, we can see that misfires are being flagged for cylinders 5,6,7 and 8. The DTC pertaining to the bank 2 camshaft position is the “cream on the plum pudding.” All of the supportive evidence thus far indicates a shift in camshaft timing on bank 2 of the engine.

Figure 1

Ryan had the sense to employ some testing techniques that were both easy to perform and delivered an abundance of diagnostic information. The resulting data from the DTC scan also guided him to the next logical test that was more involved, but would lead him to a more pinpointed answer, regarding the root-cause of the fault concerning this vehicle. Ryan doesn’t shoot from the hip with his diagnostic approach. He lets the easy tests justify the need for more involved tests (no “guess-work” — just logical, solid testing techniques).

Logic told Ryan that the results of a relative compression test would further back-up his theory. Ryan performed the test using an amp probe and a lab scope. The current flowing through the starter supply circuitry is measured and plotted over time on the lab scope. After the engine is disabled from starting and is cranked over (for a few cycles), the resulting current draw is plotted as a trace and presents as a series of “peaks.” If this Audi exhibited no mechanical fault, and because all eight cylinders are engineered the same, they should place the same load on the starter (as they approach top dead-center of their respective compression strokes). Ryan’s theory (due to the supporting evidence) is a mistimed camshaft on bank 2. Ryan anticipates a relative compression capture displaying a variation in “peak amplitude” comparing cylinders from one bank to the other bank. Figure 2 is the result of the test and confirms Ryan’s hypothesis. Ryan sees the variation in peaks but it doesn’t exactly represent the waveform he anticipated seeing. It appears to have a few back to back peaks of low amplitude and the fear is “engine damage,” sustained from the loss of camshaft timing. Ryan proceeds with yet the next logical test procedure, drawing him closer to a diagnosis and recommended course of action.

Figure 2

What would your next test be?

It’s quite clear that the engine is out of time. The questions then become:

• Is the valve train damaged?
• Is there damage to the pistons/lower end?

The questions are logical but they hold a bit more significance then they first appear to. The configuration of this engine places the timing cover on the rear of the powerplant. To even visually inspect the timing components requires removal of the front-end of the vehicle, the engine/transmission assembly and they then must be separated from one another, as the timing components are sandwiched between the two units. To replace the timing components requires the better part of a 30-hour job! Completing the repair is no easy task, to say the least. Consider the situation if the timing components were replaced, but the engine sustained damage, unknowingly!

Ryan consulted with his coworkers and most all agreed the best course of action was to recommend replacement of the engine. He knew that acquiring the resulting pressure waveforms (from the intake manifold and within the cylinders) may offer a bit of insight as to the true condition of engine overall. It may also tell him if the resulting drivability fault was simply due to incorrect cam timing or not. This of course, would allow him to offer the proper solution to the customer, and do so with confidence.

Figure 3

Figure 3 is a capture representing pressure changes inside the intake manifold. To acquire this data, Ryan affixed his pressure transducer to the intake manifold and coupled it to his PC-based lab scope. The engine is once again disabled from starting and the engine is cranked over for multiple engine cycles. What’s great about these tools and process is Ryan can acquire this data as an active file and share the resulting captures via email or through chat groups like Facebook offers, directly. First, Ryan’s concern was of the seemingly similar random-looking pressure changes in the intake manifold. He was interested in tying the results of the capture to a loss of cam timing on one bank. This is where I come in to play. Let’s analyze the waveform.

First, using a point of reference (from a known ignition event) I was able to determine when an entire engine cycle began and ended. This allows me to capture the data reflecting each of the engine’s pistons contributing to the intake manifold. Researching the firing order is necessary to determine how the activity in the intake manifold correlates with each of the cylinders. A piston chart was added to the capture to aid in analysis (and in explanation to Ryan) as to what I see occurring in the data. We have to first understand that as each cylinder enters the induction-stroke portion of the engine cycle, the intake valve for that cylinder is open. This piston will descend and inhale the fresh air from the intake manifold. Since we are viewing data from the perspective of the intake manifold, each one of these induction events results in a momentary increase in intake manifold vacuum. This causes the trace from the pressure transducer to decrease in amplitude (or “head south”). We can call these events “pulls.” We are interested in seeing which cylinder created which pull.

Cursors are spanned the entire engine cycle which offer the ability to partition the capture in to eight equally-spaced areas. These areas represent the eight cylinders contributing to the intake manifold vacuum trace. Using the cursors, I’m interested in seeing when these pulls occur, relative to the vertical cursors. A late pull will occur further from the cursor than a pull which occurred on-time. Indicated by the gray circles, these represent the pulls from bank 1. Take notice to the cursor, just left of the circle. Indicated by the yellow circles, are the pulls from bank 2. Take notice to the cursor, just to the left of the circle. If you compare the proximity of the circles to the cursors, it’s clear to see that bank 2 pulls are occurring later than bank 1 pulls. This also explains the random-looking pattern of the cranking intake vacuum trace.

Figure 4

Using a piston chart to aid in analysis and explanation, and now referencing the yellow dots superimposed upon it, it too makes it clear to see that all of the bank 2 intake pulls are late, relative to the bank 1 intake pulls. Logic supports a bank to bank timing issue, and we would anticipate every other pull to be late. That would be true in many cases, but not in this Audi’s case. Take a moment to view the engine configuration in Figure 4. The firing order on this engine’s configuration supports a firing event that alternates between banks…. except when cylinders 6 and 8 fire. They are two cylinders that fire consecutively ON THE SAME BANK! This is what you see occurring in the intake trace for pulls 1 and 2 (as indicated by the red numbers, at the top of the capture. These numbers are calling out the cylinder responsible for the pull below it. If you then reference the piston chart, you will see that I have encapsulated an area with a yellow box. This area contains two black stars that indicate when cylinders 6 and 8 approach TDC/compression consecutively. Because the bank 2 intake cam is late, the intake valves for bank 2 cylinders will open late but close late as well, leaving more volume to be shed back to the intake manifold, as the pistons approach TDC/compression. This is why the intake trace rides “hi” for so long at this point (two consecutive cylinders pumping extra volume back to the intake manifold). This is why it has that random-look to it. The appearance of the trace is due to engine configuration.

Figured that out! On to the next step

This data will tell us why the cranking intake vacuum waveform appears as it does, but more significantly, drives us further to the next logical test. A running in-cylinder pressure waveform was acquired form an easy-to-access cylinder on bank 2 (the suspect bank). The pressure transducer is used in place of a mechanical gauge and reveals a tremendous amount of data, and not just peak compression. Because the data is captured on the lab scope, with cursors we can effectively associate time with the 720-degree engine cycle. In other words, we can confirm camshaft timing (to within a few degrees of accuracy) as well as monitor the breathing characteristics of the cylinder, dynamically.

Figure 5

As can be seen in Figure 5, the running in-cylinder compression waveform (for one from the suspect-bank) is captured and annotated. The cursors denote the characteristics supporting the late intake cam timing, as suspected. The red annotation indicates low running compression for this engine. The orange annotation demonstrates the point where the intake valve opened. The cause of the deep in-cylinder vacuum (at almost 24” hg) is due to the piston descending down the cylinder with the valves closed. Only when the intake valve opening finally occurs is the vacuum relieved. Finally, the intake valve is seen to be closing at about 127 degrees ABDC of the induction stroke. These are all key indication of a late intake camshaft. The key is that the captures display what the symptoms offer as suspect. The real prize is the fact that we can see a suspect bank’s cylinder draw a vacuum and create compression with no leakage…all without disassembly and from the other side of the great Atlantic Ocean! Ryan now has the evidence to prove he may begin this saga of a repair. More importantly, he has the confidence to do so. This now perpetuated by his newfound knowledge, his understanding of the pressure waveform analysis!

Figure 6

The better part of a week goes by and I receive another Facebook video capture. Ryan completes the disassembly and confirmed bank 2 intake cam was indeed “late”. The cause of the retarded camshaft was due to a damaged VVT actuator, where the locating pin interfaces to lock the actuator in place (Figure 6). Ryan replaced the timing components and reassembled the vehicle. The engine starts, runs smoothly but the best part was Ryan’s excitement. He was dead chuffed! I only wish I could’ve been there to see the look on his fellow employees' faces!

Shortly thereafter, I received the resulting post-fix captures. The in-cylinder trace reflected strong running compression, an intake valve that now opened on-time at about 16 degrees ATDC. This allowed the piston to inhale freely and prevented the deep in-cylinder vacuum we witnessed earlier. The compression began to increase way earlier as well. The intake valve now seats at about 60 degrees ABDC. Much better than previously (Figure 7). The cranking intake vacuum waveform now exhibits pulls whose proximities are all very close to one another, regarding where they fall, relative to the vertical cursors (Figure 8). This is indicated by displaying both the YELLOW dots (representing bank 2 pulls) and the GRAY dots (representing bank 1 pulls).

Figure 7

Figure 8

We can all now see how difficult gambles can be avoided by moving forward with technology. Learning, by sharing information with peers all over the world and employing newer testing techniques that allow you to make tough calls with the utmost confidence.

Article Details

Mon, 04/01/2019 (All day)

Brandon Steckler

<p>No one person can be expert in every area of automotive repair. Expand your skill set through networking!</p>

<p>auto repair, networking, technicians, training, skill set, automotive diagnostics, social media</p>

I had (have) been writing for Motor Age since May 2000, and so, when I submitted my application for the college instructor’s job in December of that year, I included copies of Motor Age that featured my articles, and to this day, I believe my position as a contributing editor for this magazine was one of the determining factors in landing the job that a whole lot of other guys had applied for. And for those who think they want a college instructor’s job, well, you need to realize going in that it’s as demanding (and sometimes frustrating) as it is rewarding. There were times when I fully believed I had no idea what I was doing there. As of the writing of this article, I am teaching my way through my 19th year and I plan to retire at the end of May from my teaching position.

I’ll still be writing a feature or two for Motor Age every year if Mr. Meier will work with me on that front, but since I’m no longer going to be neck deep in vehicle repairs every week, I’m not sure how many more articles I’ll be able to hammer out, because the articles I’ve been writing for the past 20 years have been real stories from the service bay, and where Motor Age Garage is concerned, that’s the only kind of story that works. My time in the service bay will be limited after May, I’m afraid, and that’s where the photos and stories come from.  The point is that, while I’m not saying you’ve heard the last of me, my articles won’t be quite as regular, although, if I can write enough for Motor Age to hang on to my “senior contributing editor” status, that’d be peachy. Time will tell.

During my teaching tenure at the college, I have forged enough of a reputation with those qualified to have work done in this shop to have lots of real-world repair stories, and those are the stories I tell. Most of the customers we serve like the work we do, so they keep coming back for more, and since experience is the best teacher, my people get hammered with a lot of work, and some of it is pretty doggone tough, but that kind of pressure either molds my people into functional techs or drives them away from the profession. I want them to face tough jobs here so they can handle them out there. I consider my program to be “boot camp,” and they either pass or fail based on what they’re able to handle. My desire is for every graduate to be a living legend, but that’s more up to them than it is to me.

“It’s broke” is all they know

We get vehicles hauled in on wreckers, trailers, and yanked by chains, and sometimes when they show up, nobody even called to tell me they were coming. A couple of weeks ago a 2006 Mazda 6 showed up with the complaint that “something happened, and the timing belt came off,” which made no sense whatsoever on this engine, but then, most every service writer faces this kind of thing. Don’t get me wrong; I’m not ridiculing my customers, but for years it has boggled my mind that some of them don’t even know what year model their vehicle is, let alone which engine is in the vehicle, but that’s OK, because we can figure that out as the work order is being written. But then sometimes they’re not sure how to describe what’s going on, they just know the vehicle is “broke” and can’t be driven and they want us to work some kind of magic.

Even after sitting in the yard for a few months, this Fusion still looked pretty good after it was washed.

In the case of the Mazda, we discovered that the idler pulley bolt had broken off flush with its hole, which, as it turned out, was somewhat difficult to access. There’s a thick aluminum bracket between the pulley/spacer assembly and the hole in the block the bolt is threaded into, but the bracket is designed in such a way that the bolt passes through a long notch instead of a round hole on the way to the block. This is something of a blessing, because you can at least see the broken bolt – but on the other hand, if the bolt was passing all the way through a hole in the bracket and into the block, the bracket would probably support the bolt rather than allowing it to flex and break off.

On this Mazda, with the tire and splash shield removed, the pulley area is fairly accessible and we managed to use a left-hand twist drill bit to succeed in snatching that broken off piece of bolt out. Having worked the requisite “some kind of magic” at this point (it’s what we do, ya know), we had found the original pulley and its spacer lying in there, and so I found a suitable bolt the right length in a can of junk bolts (8mm 1.25 thread pitch), and with a new belt and that replacement bolt in place with the original pulley, we got that one going in short order.

Wait, what? Another one?

About 10 days later, a 2008 Ford Fusion 2.3L, FNR5 Transaxle with 212,564 miles showed up on a trailer. Like the Mazda, this one had been sitting in the yard until all the other pulleys were rusty and there were spiderwebs everywhere. And like the Mazda owner, the Fusion owner struggled to explain what the problem was, but it didn’t take long to figure out that this one had broken the same bolt as the Mazda 6 had. This is obviously a high mileage failure due to the flexing of that bolt.

Well, what we knew from experience was that the first thing we had to do was to get what was left of that broken bolt out of its hole, and that was a LOT harder on this ‘08 Fusion than it had been on the Mazda 6, because the broken bolt wasn’t visible at all – that spot on the end of the engine is about two and a half inches from the car body, and removing the fender splash shield didn’t help this time, because we were looking at two thick layers of steel between us and the broken bolt we needed to extract.

It has always been odd to me how we get two jobs alike within a few days of each other with such similar circumstances. Both cars broke the same bolt and both sat in the yard for a few months before anything was done about it. A few years ago we got two identical Ford Explorer Harmonic balancer failures the same week.

I know the guy whose daughter drives this car well enough that I didn’t need to call and ask him whether I could make a nice round hole in the car body to get to that broken bolt. Heck, the hole would be covered by the splash shield anyway, and it’d make the job a lot easier for the next guy. We did some tape measuring and Sharpie marking, and with a 2-1/4-inch hole saw and an arm-twisting DeWalt 1/2-inch corded electric drill, we made ourselves a nice (if slightly off center) access port, but this broken bolt wasn’t quite as friendly as the one on the Mazda had been.

Everybody who works with a drill in situations like this knows that if you spin the bit too fast, both the bolt and the bit tend to get hot, and that makes the bolt harder and the bit softer – which brings the entire job to a screeching halt – literally, since screeching is the sound the bit makes in those situations. A regular air drill isn’t the best tool for this job, because with the air drills we have, it’s difficult to control the speed of the drill. Using a drill bit extension I snagged from the local Harbor Freight (don’t cuss at me, I like Harbor Freight), we managed to use the electric drill and a new bit to put enough of a hole in that bolt to get it out with a screw extractor. Whew!

Okay, now we needed more than just a new pulley, which was all the parts store had to sell us – we also needed the special spacer that goes behind the pulley, but the Ford place had one in stock, along with a new pulley and bolt, all in one neat package for $28.

My problem with this new Motorcraft part is that the 8.8 Metric bolt isn’t (in my opinion) hard enough. If it was, these bolts wouldn’t be breaking off on more than one vehicle. On the other hand, a harder bolt might be a lot tougher to drill out if it did break. I went with the bolt that Ford included with the pulley, and when we installed a new belt, we found we needed to replace the battery, which was badly cracked around the negative cable, and we had to replace the negative cable end as well, but that wasn’t much of a problem. We checked the oil and coolant and fired the Fusion right up – after setting the tire pressures (they were all low), we put it back on the road.

Coolant leak, Nissan style

Back in 1990, I traveled to Panama City Beach with some friends for a Saturday at Shipwreck Island – we were traveling on 2 vehicles, and one of them was a Toyota van, which sprung an odd coolant leak from the joint of a steel heater hose Y on the way back, and they had to stop and refill the radiator about every fifteen miles or so. Panama City is only 100 miles from where I live (they were from Tuscaloosa), and so, that night we parked the van and I told them I would see if I could do something to plug the leak the next morning after church.

With the van jacked up and the tire and splash shield removed, I wire-brushed the place where the water was trickling out of that tee and used a bottle torch and some acid core solder to forge a repair that got them back to Tuscaloosa without a hitch, and in their eyes, I was Superman with a torch. I have since learned that Toyota had issued TSB 007 on 4-15-88 that read this way: To maximize corrosion resistance of the heater pipes on Vans (YR), the material of the heater tubes has been changed from the previous epoxy powder painted steel type to brass. That’s what the dealer put on their Toyota when they got back home, but they reported later – my repair held all the way.

This is one way to get to a tough spot – the caveat would be that, if the hole were sawed in a load-bearing place, body strength might suffer, but that didn’t look like it would be the case here.

Well, just last week about the time we got done with the 2008 Ford Fusion, a 2000 Nissan Frontier that belongs to one of the college welding instructors came to us on Friday afternoon with a coolant leak vaguely similar to the one I had fixed back in 1990 on the Toyota van. One of the heater hoses is connected to the passenger side of the engine block via a steel 3/8 pipe-to 5/8 hose 90-degree fitting, and the Nissan had just that morning began to pee coolant out of that fitting. We took a photo of the leak and zoomed in to decide if it was the hose or the fitting and determined that it was indeed the fitting after all. Furthermore, we had to remove the starter to access this fitting, and we managed to screw it out of there with a 19mm wrench. The fitting was breached from the inside by electrolysis, it appeared, and while we could have welded it, we decided that replacing the fitting seemed more apropos.

Fortunately, this part wasn’t so terribly proprietary that we couldn’t find another one – except that all the other ones we found that day had 1/2-inch pipe thread rather than 3/8. We ran out of time that first day (which was the end of the week) and so the Nissan had to spend the weekend on the lift before we could get a part, but that job ended well.

Another one bites the hook

Another regular customer came wheeling in with an F150 on a roll-back – it had sheared the driver side lower ball joint, and we had to fix that one outside the shop, but it was fairly straightforward. Get a jack and a stand under it, break out the ball joint service set, pop the old ball joint out and replace it with a new MOOG, and the rest is history.

There was also the 2004 Mercedes E320 with collapsed engine mounts that shook the whole car when you dropped it in reverse – we replaced all three mounts (both engine and the tranny mount) which took about four hours, and in the process found a bent inner tie rod, which we also replaced. Interestingly, the dealer he visited had charged him $700 to replace the upper ball joints (which bolt in, list for $80 each and total listed labor time is an hour) then they quoted him $1100 bucks to replace the two engine mounts, which (list price) are $149 each and the labor is 4 hours. Don’t know where that estimate came from. Based on list price and $100 an hour I could come up with about $750 on the mounts, but using the same standard, I could only justify about $300 for parts and labor for the upper ball joints. We don’t charge labor, but I generally have my students check dealer parts prices and labor times for grins.

About that time, a game warden came in on his 98 Chevy K2500 Crew Cab hunting truck with a popping noise in the front end, hubs that wouldn’t engage, and rear brakes that liked to skid when stopping cold.

The four-wheel drive problem on that K2500 turned out to be a missing fuse, but the popping noise was a lot more serious – the frame had cracked right at the place where the steering box mounts, and when we showed him that, he called a friend who, in his words “fixes these all the time,” but he wanted us to handle the brakes. The shoes on the driver side rear were coming apart and it needed both wheel cylinders, but first we had to bang around on the drum hubs to get those big sixty pounders off. The same rust that had attacked the frame had also tried to weld the drums to the hubs, but we made it happen with some skillful hammer work and a shot or two of PB Blaster®. The warden got new rear brake shoes and wheel cylinders, and he was good to go. By the time all these jobs were done, everybody was sufficiently hammered. A load of happy customers and students who are slightly more experienced made it all worthwhile.

Article Details

Wed, 05/01/2019 (All day)

Richard McCuistian

There was a local repair shop that had an oil change go wrong on a 2011 Kia Optima with a 2.4 L engine (Figure 1). The shop mechanic had an easy task of simply replacing the oil filter and removing and reinstalling a drain plug to drain and refill the engine with oil. The oil filter was installed properly and the correct oil type and quantity was put in the engine but the drain plug was never secured with a wrench and only hand tightened. Somewhere in the thought process the mechanic forgot to tighten the plug with a wrench and allowed the vehicle to go down the road with a loose drain plug.

Figure 1

Over time and enough road vibration, the drain plug worked its way loose and the oil started to drain from the engine. The driver of the vehicle did notice the oil light come on but proceeded to drive to get to a public destination off the roadway. Some drivers would just pull over, shut the engine off and call for roadside assistance but there are others that will not, and this sealed the fate of this vehicle. The vehicle was driven too far on oil starvation and the engine seized.

Back at the shop

The car was towed back to the shop that serviced it to find out what happened to the vehicle. The shop owner was not a happy camper because he discovered that the drain plug was missing and all the oil drained out leaving behind a seized engine. He confronted his mechanic to educate him about why it is so important to always go over your service repairs and that he would now be partially responsible on some labor involved without pay. Hopefully, this would condition his mechanic to be more aware down the road. To keep operating costs down and not go through insurance, the shop mechanic was instructed to pull the engine so it could be sent to an engine shop for repairs.

Once the engine arrived at the engine shop, they pulled the oil pan to discover a damaged crankshaft and bearings. Luckily the cylinder walls were not scored and most of the damage was lower end. The engine shop recommended a replacement crankshaft, main bearings, rod bearings and an oil pump. The repair shop decided to go ahead with the repairs that would be less costly than purchasing a used engine.

After about 2 weeks, the engine repairs were completed and the repair shop drove there to pick up the engine. Once the engine arrived back at the shop, the mechanic was eager to get the engine back into the vehicle and out of his life. After a full day to install the engine, it fired up and ran. It did not crank over instantly but it did run without any noises or signs of upper engine issues. As the vehicle ran in the bay, the Check Engine light came on, so the mechanic hooked up a scan tool to retrieve any codes to see if he left anything unplugged or not fully seated in the install process.

Whose mistake is it?

The code he pulled was a P0336 for "Crank Position Sensor Circuit Range Performance" (Figure 2). The vehicle never had this issue before so maybe something happened in the engine repair process. The engine was running so the crankshaft sensor had to be working or maybe it had a glitch in it that the ECM did not like because the wiring to the sensor seemed okay. The shop did not have a scope so they were just using old school tactics and a scan tool to figure this issue out. The shop decided to replace the crankshaft sensor with a new one and when this did not work they put blame on the engine shop thinking that they did not set up the valve timing properly.

Figure 2

The repair shop sent the entire vehicle back to the engine shop to have them resolve the issue. The timing chain and gears were checked and everything seemed in order. It was at this point I was called by the engine shop to get a second opinion.

The REAL cause

Figure 3

When I arrived at the shop I was given the whole story of events and I decided the best place to start was to hook up my 8-trace scope and look at the Crank and Cam sensors to make sense of it all. I placed my Yellow lead on the Crank Sensor, Red lead on the Intake Cam Sensor and my Green lead on the Exhaust Cam Sensor (Figure 3).

The signal patterns seemed fine with good signal amplitude and no dropouts (Figure 4) but I needed a good known pattern to compare it to. If you don’t have a good known car to hook up to its always a good idea to head to the Internet to see if you can tap into someone’s waveform library and one great place is IATN if you have a membership to access information. I logged onto their site and sure enough I was able to find a Crank to Intake Cam Correlation waveform (Figure 5). The pattern seemed similar to the vehicle I was working on and the Crank to Intake Cam correlation was identical indicating a non-timing gear issue but what caught my eye was the Crankshaft pattern.

Figure 4

Figure 5

When I zoomed into my Crank pattern (Figure 6) I counted 57 teeth between the synch gaps with an extra open gap but the good known pattern did not have this extra open gap and showed 58 teeth between the synch gaps. This indicated that there might be an issue with the crankshaft that was installed in the engine. I asked the engine shop if they had another crankshaft for this car in their huge inventory and they were able to produce one (Figure 7). You could see that this crankshaft definitely had 58 teeth between the synch gaps incorporated into the Crank trigger wheel but with no extra gap.  It was now a wait and see once they removed the oil pan for inspection.

Figure 6

Figure 7

Later in the week I drove back to the engine shop to see what they found. Apparently, someone had dropped the crankshaft they installed and caused damage to one of the teeth on the trigger wheel (Figure 8). I was totally taken back by how someone could drop a crankshaft and not take the time to inspect it thoroughly for any damage they might have caused. The trigger wheel was not a solid gear but rather a thin plate with teeth on its exterior edge. When the crankshaft was dropped it literally bent one tooth inward towards the crankshaft and the crankshaft sensor was unable to create a consistent magnetic field once it crossed its path. This created the extra gap in the crankshaft pattern that the ECM was unhappy with. The P0336 was more of a performance code than it was a circuit code and a scope would be the only option to use to actually see what was going on.

Figure 8

Once the second new crankshaft was installed, the vehicle was test driven by the engine repair shop to make sure there were no other issues with the vehicle. They wanted to make sure there was Check Engine light coming on because the last thing they needed was another comeback to bite into any profits that were left. They stood behind their work and the engine shop had to eat the labor to not only pull the engine but also to dissemble the engine to replace the crankshaft a second time. This vehicle was not a money maker for anyone involved and it only started out as a simple oil change. The only thing that came out of all of this was a valuable lesson to be learned. The vehicle was finally delivered to the repair shop and after their final inspection it was delivered back to its owner who was inconvenienced long enough without a vehicle. The owner did not request a loaner so that was a good thing but you really need to unravel how this happens in our industry.

We are in such a great rush to beat the clock and get these cars in and out for the demands put on us from our customers. Then mix this with the constant distractions in our lives or in the shop. I have seen many people working in bays actually plugged into headphones while working and it just amazes me how they can tune themselves out by doing so. I have always promoted the 5-Sense Diagnostics of Hearing, Feeling, Seeing, Smelling and Tasting while working on cars. I’m not promoting tasting but I can tell you over the 43 years working on cars I know what a few fluids taste like. It’s helped in a few cases.

The vital other four senses are so crucial when working on and diagnosing cars. Use your eyes to look at vehicles and components for anything that’s not right that should be brought to attention. Use your hearing to hone in on any noises that may not seem normal that can alert you to a problem. Use your nose to smell for anything unusual like antifreeze leaks, burnt components, batteries overcharging or even a gas leaks. Use your hands or body to feel for that miss in the engine or for the proper latching of a simple connector. The most important of all is staying focused on what you’re doing so your mind is connected to the vehicle so we don’t forget to do a simple task like making sure we tightened a drain plug. I am sure that this story will hit home with many readers out there and my only hopes is that we put our phones down in the shop and adhere to the old rules of yesteryear.

Article Details

Sat, 06/01/2019 (All day)

John Anello

When I mention “electrical” problems, I’m not referring to electronics. That’s a different topic all together in my book! To me, electrical is typically anything that’s not involving a computer. To clarify more, electrical may include the wires and terminals leading up to a module, but not necessarily the module itself. We’ll have opportunities to share war stories involving faulty electronics at some point in the future.

At almost every automotive training class I attend — and at the ones I present — at almost every trade show and at just about every technician gathering, it is inevitable someone will share (with anyone who will listen) a diagnostic dilemma in which they are currently involved or had recently encountered. It is in our nature to share them I think, but not so much to beat our chests (in most cases), but instead to possibly learn how better we can diagnose such a problem in the future. In almost every case, you’ll hear how much longer the solution took to find than the story-teller thinks it should have, had they encountered something similar previously.

Once disassembled, it’s obvious the electrical contacts could not conduct well, much like a starter solenoid’s contact disk that is worn.

I’ve not seen everything there is to see and I pity the poor soul who thinks they have when it comes to automotive electrical problems. I attend as many training events as I can in part to hear other people’s war stories. My feeling is, if it happened to that person, it will likely happen to me as well and when it does, I’ll have an advantage – that I learned how it was solved without suffering the pain and agony that the other person went through! I am a member of many automotive technician websites for the same reasons.  There’s no logical reason for me to work harder than I have to. Is there one for you?  

In my classes I try to emphasize the importance of understanding the concepts, the strategies and the principles of operation rather than to focus on how any one manufacturer has applied those to their products. What I mean is, for example, it’s great to know how a GM TPS (Throttle Position Sensor) works, and it’s important to know how to properly test it. It’s as important to know where each one may be located on the various applications ONLY if the majority of vehicles on which you work are manufactured by GM.

However, most of us do not work on only one brand of vehicle. So, if you know the principles of operation for a GM TPS, for example, then no matter which manufacturer employs a similar device, you should still be able to apply the concepts learned about the GM TPS to the one you are working on today. There are rare exceptions but a majority of TPSs, a majority of starters, a majority of fuel injectors (etcetera) — all share the same concepts. Master those concepts and apply them to whatever you’re fixing today to be considered a great diagnostician!

Applying electrical principles

I recently had an opportunity to put my own instruction to the test on a non-automotive application. Some good friends, a married couple, had called a residential heating and air specialist because their home HVAC (Heating, Ventilating and Air Conditioning) unit would blow air properly but not always at the correct temperature. The HVAC technician spent less than a half an hour after arriving to inspect the unit before presenting my friends with the recommendation to replace the whole thing. He claimed it was very old and inefficient and said he’s not familiar with that brand, then said he wasn’t trained on them anyway. It didn’t cost anything for his service call nor for his writing an estimate for replacing the unit (thankfully!). I suppose we consider 1999 cars as “very old,” which is the same year this HVAC unit was produced. I’ll give the tech that much.

When my friends told me of their dilemma and what the tech had said, I just shook my head in shame, knowing a lot of automotive technicians say similar things to owners of vehicles on which they were not trained. The HVAC technician could have applied the same concepts he knew to this (well-known) brand, but apparently didn’t have confidence in his skills to attempt such a thing. It seems more of us at least attempt to apply the principles of operation on vehicles we may not be familiar with.  The HVAC technician never even tried.

(Image courtesy of Mitchell 1) It was rare to see isolated circuits when you wanted to look at a wiring diagram for a vehicle in 1980. This diagram is four pages — for the whole vehicle!

Being the brave soul that I am, I told my friends I’d look at it and see what I can do. I started by researching the complaint for the brand and model on a few DIY home repair and HVAC websites. I wanted to see if there was something that went wrong commonly with units that were similar to my friends’. This is no different than one of the first steps I’d perform when researching an automotive problem on a brand with which I was unfamiliar. Do you use websites like iATN, Identifix, Diagnostic Network, etc.? I find these extremely valuable especially under the same circumstances.

I didn’t have any good luck. There weren’t enough identical complaints/fixes for me to condemn any particular component based on a common problem. There were no silver bullets for me here. I had to consider doing what a good HVAC technician might do – diagnose it!

My research led me to the manufacturer’s website where published were the complete wiring diagram, the Owner’s Manual, a Quick Start Guide and get this, an installation manual complete with a troubleshooting guide! How about that? This very old unit has built-in troubleshooting complete with blink-out codes!

You younger folks might not appreciate my excitement, but having been present when cars were finally equipped with self-diagnostics, it completely changed the much-lengthier diagnostic processes we had to perform prior to that improvement! Imagine what we went through when working on computer systems that were not equipped with a way to direct you to a system, let alone a component that may be faulty?

As typically happens when working on cars with an intermittent fault, when I arrived to look at the HVAC unit, it was working as designed. Also as expected, this very old unit had no ability to store codes, just like the very old cars that erased codes when the key got turned off. This is where my diagnostic instincts came into play.

The manufacturer listed the part as “obsolete.”  Another supplier had similar components which were rated at a higher load capacity than the OE.

I looked at the wiring diagram to understand the circuits – excluding the air distribution section (remember, the home owners said it continued blowing, just not always at the desired temperature). In the diagram was a compressor “Contactor” which looked similar to the way a car’s starter solenoid would be wired. Knowing how an intermittent “No Crank” complaint was sometimes attributed to the starter solenoid I headed in that direction.

With BOTH circuit breakers tripped, I removed a service panel. Once the unit’s cover was off I performed a visual inspection and saw almost every serviceable component well within reach – unlike what we encounter on cars – and in plain view was the Contactor and just about everything else. It was obvious there had been a lot of arcing of the contactor plate, which required no disassembly for me to measure voltage drop across the circuit when operated. I carefully attached the best meter I have to the terminals on each side of the Contactor, then I operated the compressor repeatedly while observing the meter’s readings (from a distance – I don’t like 220 Volt systems). Not once in the 10 times I turned it on, did I see the same voltage on each side if the contactor. Just like when a starter solenoid fails, the contacts had worn out!

The original equipment (OE) manufacturer had stopped making that part several years ago and listed it in their catalogs as obsolete. I found two aftermarket Contactors that were the same size, same shape, had the same number of terminals but had a higher amperage rating than the OE part. I bought them both for less than $50, including shipping. After verifying identical circuitry to the HVAC unit, I installed the better-looking (higher quality) Contactor and ran the same voltage drop test again. This time the test results were identical, every time, I was confident their unit would work as designed for many more years to come. I like to verify that my test results differ from previous readings after a component replacement. Do you?

Optional capabilities are often enabled on a residential HVAC system simply by attaching a wire to the correct circuit board. This damaged wire terminal required replacing but once attached correctly, the option worked perfectly.

To date there have been no more complaints of intermittent operation. As a side note, this HVAC unit had an optional feature that could have been enabled had the wire terminal not been damaged that allows the feature. I replaced the terminal, connected it appropriately and have some very happy (and comfortable) friends again! I’m not a HVAC technician but I was able to accurately apply the concepts I learned in the automotive repair trade to successfully repair a residential HVAC unit.

Principles of induction

I was a dealership diagnostic technician who was presented with a particularly challenging diagnostic dilemma in one memorable diagnostic battle that occurred early in my career. One of the first redesigned Chevrolet Corvette models to be delivered to the public (at that time) had been purchased by the dealership’s owner’s son. The car returned with an A/C blows warm air complaint in less than a week after initial delivery.

The compressor fuse had opened the circuit it protected, but whatever had caused it to do so was not evident. A new fuse was installed and the car returned to its owner. Within a week the same thing happened, with the same test results and the same repair. You know what happened again, yes, the car returned. I was instructed to locate the cause and to repair it before taking on ANY other job. When you work in a flat rate environment, you do not like hearing instructions like that, ever!  Knowing it was the owner’s son’s car also made this job extremely important.

(Image courtesy of Mitchell 1) “Page two” - Mostly interior wiring, including the Alternator and the AC circuits mentioned in the article.

In the early 1980s we didn’t have all the fancy diagnostic tools that are available today.  What I had to work with were made by Radio Shack, Sears & Roebuck and a few miscellaneous items bought from tool truck vendors. Does that give you any idea what kind of challenge this intermittent fault presented?

In short, at the 10-hour (into it) mark, my service manager enlisted the assistance from techs at other dealerships. I knew how to reproduce the blown fuse but we couldn’t determine what was causing it. The blower had to be in M2 speed, the third fastest selection, for about 15 minutes but visual inspection of the circuits involved did not reveal any shorts. We isolated wiring, jumped circuits, replaced several components, etc., etc. with no positive effects.

At the 20-hour mark, (over the phone) assistance was requested from the GM engineers.  We followed their directions to no avail. At the 30-hour mark, two instructors were flown in from a GM training center several hundreds of miles away. They flew back by the end of the week dumbfounded. After that, two engineers were flown in from either Bowling Green, Ky., or Detroit, Mich. (or both, I don’t remember).

Meanwhile, not having received a decent paycheck since this job started, I was getting poorer by the week. These two gentlemen came on the scene like gangbusters, were full of ideas (none of which hadn’t been tried yet) but after the fourth full day, were as flabbergasted as all the rest who had touched this car. They went to lunch with the service manager and for a change, I left the premises too. I went to a nearby park, sat under a tree and processed everything that had been done over the past several weeks.  I got away from the car – and figured out what was causing the problem.

Upon arriving back from lunch the engineers were not sure in which direction we would proceed. I told them to go to their respective homes and that I had it figured out. Of course, everyone was excited and wanted to know what was causing that fuse to blow. I refused to say unless I was guaranteed to receive payment for every hour I had invested (by then, 48 hours!). At first the service manager balked, said something about not being able to promise that.  I replied there were several thousands of these cars built the same way that will dumbfound a lot of people — and if THAT wasn’t worth the money I should have earned then I was walking! The engineers convinced the service manager to change his mind.

You’re wondering too, aren’t you? Here we go...In M2 speed, the blower resistor is using all of its resistors, glowing cherry red. A lot of amperage is flowing through that circuit.  At that blower speed, with all the windows closed, after about 15 minutes the low-pressure side of the air conditioning system drops and the (axial) air conditioning compressor cycles off. When it cycles back on, the total amperage requirements of the alternator exceeded the voltage regulator’s abilities to work properly.

This vehicle was equipped with an Amp gauge which was wired IN SERIES with the alternator output. Between where the heavy (10 Gauge?) wiring passed through the “Firewall” (Bulkhead) connector to and from the Amp gauge, was located the air condition compressor clutch circuit wire. It was basically sandwiched between both of the Amp gauge’s wires.

During the momentary alternator overload condition, amperage was induced into the A/C compressor clutch circuit — which subsequently caused the fuse to blow (open the circuit). Relocating the smaller wire in a different position of the bulkhead connector solved the problem.

I repeated the blown fuse, and proved the repair, multiple times for the benefit of the engineers before they left. Like I mentioned earlier, I want to test the repair repeatedly in order to confirm the problem is fixed. I got paid for every hour I invested in that car and never forgot about induction again. I’ll bet those two engineers didn’t either!

Article Details

Mon, 07/01/2019 (All day)

Jaime Lazarus

<p>You will never forget the tough diagnostic dilemmas, whether won or lost. Let me share a few of my most memorable with you.</p>

<p>automotive, electrical, diagnostics, repair, Jaime Lazarus, Motor Age</p>

My friend, who happens to be a fellow amateur radio operator, sends me a text message with a picture of a scan that has been performed on his 2012 Ford Fusion and asked, "Do you have a few minutes to help me find out the problem with my car?" He goes on to say, "Check engine light is on for a P0420. I'm sure it's just O₂ sensors."

I'm usually cautious about volunteering information over the phone about what could be wrong about a vehicle when I haven't had my eyes, ears, or at least some scan data from the vehicle. I get even more cautious when my ham buddies, who are a lot smarter than I, ask me for input.

The subject vehicle is a 2012 Ford Fusion with 87,000 miles and an automatic transmission. The MIL is on, it's running rough and has poor performance.

I don't have the confidence that I should when it comes to automotive diagnostics. I've been wrong more times than I can count and I don't want to be stuck with a nightmare I can't fix — especially when it's on a friend's car and when it's a "routine" P0420. When I look at catalyst efficiency codes nine out of ten times the ECM identifies a faulty catalyst. The ECM may hint at the reason why it failed with other DTCs but most of the time. We're left to find the reason why the cat failed on our own.

Sometimes we get unlucky enough that the replacement converter doesn’t fix the catalyst code. That is going to be a bad day for everyone involved.

OK, let's go for it!

There are five basic quick checks that I want to perform when I see a P0420. Those quick checks include identifying any current misfires or misfire history, identifying any fuel trim problems, validating the downstream oxygen sensor voltage, confirming that the downstream oxygen sensor is switching and searching my service information for software updates and/or common problems.

So I ask my friend, “Do you think this car has been misfiring before the MIL came on?" He believed his vehicle didn't start running bad until after the MIL came on and it's not always performing badly. It's an intermittent performance issue. That's backward from every other situation I've ever seen. Usually, it's running bad and then the MIL comes on with a catalyst efficiency code.

An auto scan of the vehicle confirmed that the only codes present in the ECM are a P0420 catalyst code and a p1000. For those of you who haven't seen a p1000 on a Ford product, it means the ECM has not completed all of its monitors. This is a really good hint that someone has been clearing codes before you worked on it. If he cleared the codes, he also erased any potential misfire history and Freeze Frame data that may have been stored. So at this point, I have to trust that if I cannot duplicate a misfire on my test drive or in the bay it didn't have a misfire. At this point in time, if the cat does prove to be faulty, I don't think a misfire is the underlying cause.

The next of my quick checks is to identify any fuel trim problems. Fuel trims problems are a bit subjective. What I mean by that is some technicians or instructors say that plus or minus 10 percent is ok, others say plus or minus 5 percent. When I have analyzed newer cars without problems, they are closer to plus or minus 5 percent in my experience.

I checked fuel trims and trims are darn near perfect plus or minus 5 percent even under load. It's important to check fuel trims during a road test in all operating ranges in order to rule out a trim problem. Like the misfire monitor, the fuel monitor is continuous and fuel trims can be off in one rpm/load range and just fine in others. I don't think a trim problem ruined the catalyst.

So I move on to my next batch of data. I start the car to warm up the cats at 2500 rpm for a few minutes and I watch the downstream 0₂s. The bank 1 downstream 0₂ is switching very rapidly, indicating the catalyst can no longer store oxygen. At this point, I agree that the cat is faulty but what caused it? I still haven't identified the performance problem either. I do know that my downstream oxygen sensor is not skewed low by an exhaust leak because it is switching from 0.1v to 0.8v. In my experience, a cat code set by an exhaust leak post cat will suck air into the exhaust and pull the downstream 0₂ low due to a high amount of oxygen in the exhaust.

After the MIL has been addressed I start to focus on the drivability problem. There were two big hints that led me to the path I chose next.

When I went for a drive I did a couple of WOT runs and I felt like the car had power but it just wasn't all there. The only reason I picked up on this is that my fiancé happens to have the same car which I drive frequently. This lack of power wasn't much but it was noticeable.

The second giveaway is the lack of a 1-2 shift under heavy throttle. I'm not saying I put the engine's safety in jeopardy but trust me it wouldn't upshift. I thought to myself at the time, this is going to be an expensive bill if he's got a transmission problem and bad cats. And then it hit me. I need to do a Volumetric Efficiency calculation.

Is this a breathing issue?

A VE test is used to identify breathing restrictions, or more precisely, it helps identify any issues with the engine's ability to take air in and get it out again. A volumetric efficiency test compares the total theoretical air charge an engine of a given displacement should be able to take in to what it actually takes in, and expresses it as a percentage. After all, an engine is really just a big air pump.

I recommend running the numbers several times with scan data to accurately average the data. To perform a VE test, you're going to need a safe testing area near your shop where you can safely perform a WOT pass, starting from a slow roll in first gear and continuing right up to the 1-2 upshift. You'll also want your scan tool plugged in so you can record mass air flow in grams/second, intake air temperature and engine rpm. Graphing is better than recording the data numerically. It makes it easier to pick out the numbers you'll want for the next step.

Notice the rise in intake air temperature during this VE test run. Why is the air in the intake getting hotter when it should be getting colder?

You then put these numbers into a VE calculator. Many are available online — just "Google" it. During the 1-2 shift, the engine will be at its peak breathing range. With the car I was working on, I had to manually upshift this car to avoid engine possible damage due to over revving. What I saw in the scan data was very exciting to me!

A rise in intake air temperature during acceleration! I had never seen this before…ever!

Sometime ago, probably in early 2017, John Thornton was doing a class and this topic was brought up. I'm blessed to have had the opportunity to attend his classes. The conversation I had with John about rising intake air temperature was a side note in his class. A side note! I'm telling you this blew my mind. One thing about John if you have ever had him as an instructor is he is so humble, so intelligent, so dedicated but also just so simple sometimes. When he spoke of this technique a couple of my classmates were just mind boggled. I've only been working on cars for about six years now but I've done hundreds of VE calculations.  Not once did I ever think to look at intake air temperature closely.

"On a good car," (and I'm quoting this from a text John and I shared), "I expect intake air temperature to decrease as air mass increases." How many times have I seen this and paid no attention to it? Hundreds of times I've seen this during VE testing. I never thought about if intake air temperature increased with a rising air mass that it would mean something - or be a useful diagnostic strategy!

What does it mean??

Intake air temperature drops under acceleration because the engine is breathing in lots of cool air and it cools the intake air temperature sensor and the engine. So if intake air temperature increases, we have a restriction preventing the engine from bringing in cool air. This restriction could be an intake restriction or an exhaust restriction. I suspected an exhaust path restriction due to the ECM setting a P0420 and the scan data evaluation.

Always prove the fault

I prove this another way. I've written before about testing your hypothesis two ways to fact check yourself. I’m already counting three different data points to condemn the cat. But I want to see if I can dissect this a little more. See the ECM didn't set a p0430, it only set a p0420. So I anticipated that the restriction was on the bank that set the cat code. I was wrong in that anticipation. The exhaust path restriction was notated on both banks, as you can see in my in-cylinder running captures with a pressure transducer. When I do a snap throttle test, both banks exceed 30psi on the exhaust stroke. So if my ECM is OK with my Bank 2 cat but there is a restriction noted on both banks, where is the problem?

Prove your fault with more than one test before pulling the trigger on a repair. In this case, I'm going to measure backpressure on both banks using an in-cylinder test.

Both banks built up in excess of 30 psi on my snap throttle test. Exhaust restriction confirmed!

In the rear catalytic converter. Like many V-6 and V-8 designs, there are three catalytic converters in the exhaust — one at each manifold and one downstream after the Y-pipe. The Bank 1 cat's ceramic, mounted to the rear manifold, broke apart and ended up clogging the rear converter almost completely.

The technique that John mentioned in his class really helped me with this diagnosis for one simple reason — understanding what a known good VE calculation for this engine? For a long time, an acceptable VE calculation range was 75 percent-90 percent.

The Bank 1 cat (the one with the P0420 code) had a failed ceramic that broke apart and clogged up the rear cat on its way down the exhaust path.

What I want to focus on here is when I ran the numbers and averaged my VE calculations I was coming up with about 75 percent. Not too long ago this number was in an acceptable range and I may have blown it off and moved on, looking for another reason for the drivability complaint.

On the verification test drive, intake air temperature behaved more normally — cooling instead of heating up.	So this one caused the DTC and led to the cause of the drivability problem.

The only way you would really know is by collecting known good data. The data for me happened to be sitting in my driveway when I got home. Sometimes we get lucky but at other times we are waiting for information. In this case, using the technique that I recently learned to help me get to pinpointing the problem much quicker because I didn't immediately have a known good. Next time you’re on a road test for a low power complaint grab your intake air temperature and absolute load PID and some downstream oxygen sensor data, and you should very quickly be able to identify a restriction in the exhaust!

Article Details

Thu, 08/01/2019 (All day)

Timothy Jones

<p>When working on a friend&rsquo;s car, I don&rsquo;t want to let them down. It is a lot of pressure to ensure my diagnosis is accurate the first time!</p>

<p>P0420, Ford Fusion, DTC, catalytic converter, intake air temperature</p>