Heading Off Comebacks And Other Tales

Aug. 28, 2014
The first story shares a lesson on not getting caught with your pants down, the other is a tale of a BMW clutch gone sour, and the third? Well, the third is just for your enjoyment! 

I have a few stories from the shop to share with you this month. The first shares a lesson on not getting caught with your pants down, the other is a tale of a BMW clutch gone sour, and the third? Well, the third is just for your enjoyment! Let’s get to it.

A Leaking Lincoln A new customer shows up at our door with a 2002 Lincoln LS (3.0 liter) complaining of a drivability issue and an illuminated Malfunction Indicator Lamp (MIL). Connecting our shop scan tool in Global OBDII mode found System Lean codes (P0171, P0174) for both banks stored in the Engine Control Module’s (ECM’s) memory. But when I check for codes and related data, I don’t stop after checking the initial basics. Look closely at the screen capture in Figure 1. Do you see what I saw?

If you noticed the red warning that not all of the monitors had run since the last time the codes were cleared, you did see what I saw! In fact, to avoid being burned by a comeback I didn’t cause, I make a habit of checking the monitor status on every car we service.

Why? Because the MIL light might return after my repairs and after the missing monitors run. Always remember that some codes, when set by the ECM, might cause testing in other systems to suspend until they have been corrected. As a tech, you perform flawlessly and repair the original cause only to have your customer come back a day, a week or even a month later with the MIL back on. And all they know is they already paid you to turn that irritating light off once already. They don’t want to hear, after the fact, that ii is caused by a whole ne problem. Learn the lesson I learned: If the monitors aren’t all done when you get the car, advise your customer then and there that another problem might be hiding behind the one they came in with.

A quick look at Freeze Frame data and check of fuel trims at idle and at 2,500 rpm told me I was looking most likely for a vacuum leak as the cause of the System Lean codes. The fastest way to find out where the leak is, is to smoke the intake system, and our smoke test pinpointed the leak to a failed PCV elbow. Not uncommon for these engines especially when they have some mileage on them.  The repair went without a hitch and I cleared the codes and took the car for a test drive.

Upon my return, I rechecked the monitor status and looked for pending codes (or first time failures that won’t turn on the light until the second failure). Sure enough, all but the EVAP monitor was complete and a new code was waiting its turn to frustrate its owner, a P0420 Catalyst Efficiency Below Threshold.
Good thing I had this all documented ahead of time!

Curing An Old Beemer
By Pierre Respault, TST VP

This older BMW came into a friend’s shop with a host of complaints: erratic shifting, slamming into first and several dash lights on. Codes were found stored in the ECM including secondary air only on one bank, low voltage in several controllers and clutch position sensor faults. The vehicle had been sitting over a year so for the time being I ignored the voltage codes.

This vehicle is equipped with a standard transmission that is computer controlled. When I scanned the transmission live data, the clutch position Parameter Identifier (PID) was extremely erratic with the engine running, but steady Key On Engine Off (KOEO). Our BMW service info said the clutch slave and position sensor were supposed to be replaced together. The slave has studs in it and the nuts are inside the bell housing, so the transmission has to be removed.

The clutch slave plastic end, fork and TO bearing were badly damaged, but the ultimate cause was popped rivets in the pressure plate. Notice the two rivet heads missing at the top and upper right positions (Figure 2).

In Figure 3, you can see the pressure plate’s fingers are out of plane. This is why the feedback from the sensor was so bad and why the computer wasn’t able to correct for the problem. I doubt the sensor itself was bad, but we followed BMW procedures and replaced the clutch, fork, pilot bearing, slave cylinder and sensor. This system needs to be initialized with a factory level scan tool or it will both not work correctly and destroy the clutch in a short time. After the repair, it shifted perfectly.

Out Of Sight?
By Pete Meier, technical editor

Next time you're making the drive into work, take a moment to observe the cars around you. How many do you see that have every window rolled up tight in an effort to keep that nice air conditioned air inside (or to keep all that winter chill outside, depending on the time of year)? And cars made in the last 15 years or so seal so well you can almost feel the pressure change as you close the last door.

I think you'll come up with the same observation as I have. Most drivers like their cars sealed tight. Only one problem with that: contaminated air.

Did you know that unfiltered cabin air could be nearly six times more polluted than the air outside the car? And by pollutants, I mean things like pollen, dust, mold spores, diesel soot and smog.   But that's not a problem for about 85 percent of the cars made since 2006. That's because they are equipped with a high tech device used to clean up that incoming air.

The cabin air filter.

First introduced in Europe in 1987 in an effort to protect passengers from pollen and dust, they quickly evolved to include traffic related emissions like diesel soot and smog. But the idea really didn't catch on in the United States until the mid-1990s, and even then it was primarily used on the higher end of the OEMs offerings. 

Cabin air filters have come a long way in a relatively short time. Most filters are able to filter out particles as small as 3 microns, with top-of-the-line filters able to screen out contaminants as small as 0.001 microns. To put that in perspective, a dot made with a sharp pencil is about 200 microns in size. 

Cabin air filters not only play an important role in reducing airborne contaminants. As a side benefit, they help keep the A/C evaporator clean and that helps reduce the potential for mildew and odor as well as insure peak cooling performance. Left alone, a clogged cabin filter can impact A/C performance (by choking off air flow to the EVAP) and in some cases, has resulted in A/C compressor damage.

As techs, we understand the need to keep the engine's filters clean and maintained. When was the last time you checked to see if your customer's car was equipped with a filter for the air they're breathing and inspected its condition?

No, cabin filters are not just an add-on sale. They are as much a part of routine maintenance as servicing any other filter on the car.

Sponsored Recommendations

ZEUS+: The Cutting-Edge Diagnostic Solution for Smart, Fast, and Efficient Auto Repairs

The new ZEUS+ simplifies your diagnostic process and guides you through the right repair, avoiding unnecessary steps along the way. It gives you the software coverage, processing...

Diagnostic Pre- and Post-scan Reports are Solid Gold for Profitability

The following article highlights the significance of pre-scans and post-scans, particularly with Snap-on scan tools, showcasing their efficiency in diagnosing issues and preventing...

Unlock Precision and Certainty: TRITON-D10 Webinar Training for Advanced Vehicle Diagnostics

The TRITON-D10 lets you dig deep into the systems of a vehicle and evaluate performance with comparative data, systematically eliminating the unnecessary to provide you with only...

APOLLO-D9: Trustworthy Diagnostics for Precision Repairs

The APOLLO-D9 provides the diagnostic information and resources you need to get the job done. No more hunting through forums or endlessly searching to find the right answers. ...

Voice Your Opinion!

To join the conversation, and become an exclusive member of Vehicle Service Pros, create an account today!