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Surviving the tough diagnostic challenges

Thursday, November 1, 2018 - 07:00
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Seriously, the reasons why I don’t want to perform the replacement of mechanical devices is two-fold; first, I get bored easily — so the tasks I perform become “tedious boredom” when all I’m doing is trying to get them done faster than the last time I did the same thing and secondly, I’m no longer physically able to do what I used to be able to do. Maybe it’s because I did what I did when I was able to, with disregard for how I’d eventually PAY for doing them in the future, is why my body has fallen apart? It’s as good a guess as any. So, it’s diagnostics and ONLY diagnostics for me now and in my future, sanity be damned!

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2005 Chrysler 300 (LX) - The vehicle

There have been many people credited with coining the phrase “The definition of insanity is repeating the same mistakes and expecting different results.” There are many variations of that often-repeated statement and they all seem to apply most appropriately when we are diagnosing problem vehicles! How many times have you thought “Did I miss something in my diagnosis?” It’s that question which I kept repeating recently while I was diagnosing a 2005 Chrysler 300 LX with a 5.7L Hemi, AWD and 80,985 miles on the odometer. Have you ever had to re-do the diagnostics you performed previously because a problem is still present?

2005 LX Engine Compartment

Starting with the customer’s notes

As was the case with this vehicle, we aren’t always fortunate enough to be able to review repair history. Jeff and Katie had purchased the vehicle five months before bringing it to Gary’s shop. They said it had only recently developed the symptoms regularly when at first, they were happening only sporadically. As described by a written note left in their vehicle, the symptoms included “drives rough — jumpy — all the time, worse when wet.” They went on to describe them further by writing “does sometimes cut out when stopped. Not running on all cylinders. Spark plugs replaced 2 months ago — problem is worse.” Lastly, it was written “Get random misfire errors.” I just love customers’ notes. Don’t you?

Do you ever get the feeling someone has been working on a car, recently, like right before the customer brought it to YOU? That’s the way I interpreted what was written. Is that what you thought too? My curiosity was peaked around HOW the customer knew there were misfire codes. Also, I had to believe the REASON the spark plugs were replaced was to (guessingly) resolve the misfire(s) because the cause could not be determined.  Obviously that work made things worse (or did it?). Did rainy weather have an effect before the spark plug replacement or did this operation create a new problem? I also wondered WHO replaced them (a professional or amateur?). Lastly, what was meant by “sometimes cut out when stopped?” It was my responsibility to determine the causes of these complaints.

I preach about the need for your first step to be a visual inspection, which is where I started on this vehicle. Until this one, I’d never worked on a 4WD Chrysler product that didn’t have “33 inch Mudders” and wasn’t extensively modified for off-road use only!  This was a new one on me so I was particularly observant!

The first thing I noticed was a much-labored starter when cranking the engine. There was a noticeable “starter drag” but the engine did eventually start. Once running, a light tapping sound was heard, which went away after a few seconds. The lead tech and I went out for a test drive. We noticed a loud “rubbing” noise, similar to a tire rubbing the inside wheel well as we backed into the parking lot to leave. It went away as we took off. No misfires were detected while driving the vehicle “normally” and all systems operated as designed as long as we drove in that manner. But this car’s got a Hemi!

Radical! But not in a good way!

When traffic permitted, we tested how well the Hemi performed. Yes, tested. Hard. It was when the transmission was about to shift into second gear (and again later when it was ready to shift into third and when shifting into fourth) that there was what can only be described as a radical event. It was as if the engine’s controller suddenly forgot how to do so. There were backfires out of the exhaust. There were backfires under the hood. There was bucking and jerking. There was almost a loss of vehicle control every time we put the car to this “test.” It was violent. It was engine load-related we agreed, since it didn’t matter what gear we were in, what speed we were going, etc. I decided to record as much as I could with the scanner (wiTECH) but under such conditions, it’s difficult at best to capture events like these let alone hang onto the laptop! We made it back to the shop without a law enforcement escort.

I begin scan diagnostics with a complete vehicle network test whenever I can. Chrysler’s wiTECH software displays the vehicle network graphically and indicates which modules have DTCs, have updates available and more.

The engine sounded “louder” than it should be, as if there was a modified air intake, each time we accelerated. Sure enough, it had been modified, but not like you’re thinking. There was no air filter installed, and the air filter box lid, to which the air snorkel attaches, was not clamped down tightly. There was no sign of where the air filter might be. Does this information make you think (like I did) that the spark plugs might not have been replaced by a professional? My visual observations revealed no more surprises.

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