Hi All,

Started up my 2004 A4 3.0 this morning, and misfiring was so horrendous that the engine barely managed to idle. Misfiring was so bad that my first though was that perhaps the timing belt had jumped some "teeth" (the belt is in need of change and is on my list of things to do or get done...it has somewhere between 85k and 150k).

Codes only showed misfires:
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - - MIL ON
16688 - Cylinder 4
P0304 - 001 - Misfire Detected - MIL ON
16689 - Cylinder 5
P0305 - 001 - Misfire Detected - MIL ON
16685 - Cylinder 1
P0301 - 001 - Misfire Detected
16687 - Cylinder 3
P0303 - 001 - Misfire Detected - MIL ON
Readiness: 0110 1101

Against my better judgement, I decided to let it warm up, and after a few minuets, all misfiring went away. After clearing codes, they did not come back, but I have not tried restarting it while cold yet (tomorrow will tell).

Audi replaced all the coils about 37k mi ago (recall issue), so I would not think it was the coils. Nor would I think they would all go bad at the same time without any signs of previous misfires (I did see other misfires on other cylinders than those above while engine monitoring). I also replaced a failed fuel pump and filter not that long ago (~50k).

Any ideas what might cause such extensive misfires at cold start up?

Thanks in advance!!

 

I'd track down the main connector for all the coils, and disconnect/spray clean/reconnect it. That connector might be in the ECU box for all I know, but it sounds like coil power or ground became marginal, probably at one connection.

 

Thanks turbo510! That sounds very likely, as the day before I was driving in rain, etc. I originally tried to trace the coil connectors thinking it might be something like you mentioned, but they soon disappear in the engine morass. I will see if I can find out where they connect and clean as you recommend.

The problem has not reoccurred, but it would be nice to know the cause. If anyone has a picture or description of where the coils connect to the ECU (or whatever it is), it would be greatly appreciated!

Cheers