Mrg02D

As a continuation of my other thread about my dealer taking 1.5 months to fix some oil leaks, I figured I’d start this to talk about a new problem:

PSM failure and Auto Start Stop warning lights while driving. Had message about taking it in and it being okay to drive also. Car went into limp mode and was shaking badly while I got off the interstate. Upon restarting the car, everything went back to normal and drove home fine.

Sounds like a bad coil? The timing is suspicious as I just got my car back the day before this happened.

I don’t have a scan tool, so I don’t know the errors...Dealer doesn’t open until tomorrow, but I’m guessing they’ll claim it was a coincidence if it turns out to be a bad coil.

When I got it home, I stuck on my trickle charger and noticed it was very low. Maybe it was the battery after sitting for 1.5months?

RAudi Driver

A failed coil pack will not put the car into limp mode. It will make it run on one less cylinder, which would cause shaking and loss of power. The battery is always the first culprit if the car has been sitting. Hit that first then, if it's a coil pack, I have one that you can have for free if the turbo's fit the S models.

Mrg02D

Drove to work today without any issue. Revs were good and idle is smooth.

Hopefully it was just the battery being low as I don’t want to give it back to them any time soon :-)

Once a coil begins to fail, would it stay problematic or could it behave itself for a bit (turning off the ignition cleared the problem)? My Cayenne was built in Nov 2014, so the coils are pretty old now. Plugs were done 20k miles ago. If it happens again, it may be worth just replacing everything?

edit: Took the Cayenne to my Indy for a scan. Found two cylinders had misfired. Nothing else. Indy doesn’t think there’s any need to worry, just to watch if it happens again.

Bad gas maybe? It sat for 1.5 months and I filled up at Costco right before the “happening”.

Drove it a little rougher than I usually do to see if anything felt out of sorts...Got boost up to 1.1bar and it sure felt strong. Smooth idling and Auto Start/Stop working fine. Feels smoother and more responsive after the two leaks (timing cover and RMS) fixed.

twodollardoug

Same symptoms mine had when #3 coil failed. Then cleared up, and drove fine. But then it came back. I bit the bullet and replaced all 8 coils. And put two of the old good coils in the trunk. Just in case.

Mrg02D

About how long before #3 failed?

twodollardoug

I don't know, I replaced it after the second event. It was only 2 or 3 days between events. If you end up replacing them, mark them. That way you can keep a couple for spares. Remember when you order them you need to order the hold down bolts also, they are one time use. Order a few extras for your spare coils.

Mrg02D

It happened again. This time, I had the car revved up really high after paddle shifting in heavy traffic (in anticipation of having to quickly pass someone). Didn’t realize I had it revved so high as I was watching traffic.

I was able to maintain speed in the 70s this time and pulled off the road. A quick on/off/on got everything back to normal.