beachcomber

I have been searching the forums and found posts indicating it is near the windshield washer fluid reservoir and others suggesting to follow the coil harness wires, but for the life of me, I can't find them.


I have a misfire on Cyl 4 and want to swap the 2 Ignition Control Modules/Power Output Stages to see if the misfire remains with Cyl4 or moves with the swap.


Thank you for any information you can provide. Apparently a picture would help me even more
Thank you,
Beachcomber
2008 A8L 4.2

Mister Bally

Another great example of a reason to buy the service manual for this vehicle.

I can't help much as I am nowhere near my pc that has the manual installed on. Basically, remove the black plastic covers in front of the windshield. You will find it/them. Them for the non4.2 L engine models. It for the 4.2

beachcomber

Agreed. That's why I purchased the manual and VCDS. Been searching the manual- problem is that I don't see anything in the manual showing the location.
Thanks!

GradecEngineering

Just curious, what have you done so far to diagnose your issue? Have you replaced the #4 fuel injector already?

beachcomber

I have not replaced the fuel injector yet. I wanted to try the POS (no pun intended) swap first I've read that there is a good chance this is my issue.


I have swapped plugs and coils. Misfire remained with Cyl 4. I should clarify that the misfire is on cold-start for about 1-2 min. Once the car is warm, I do not detect any misfires.


Thanks for your suggestion! I will try that after the POS swap.

MP4.2+6.0

If it stayed at cylinder 4, aren't you already past the ignition coil questions? Seems to me you are now at one of bad plug, dirty valves maybe, or injector, with the 1:1000 usual caveat about things like ECU.

Suggest:

1. Look at service history. If past 35 or 40K miles on last plug change, I would just do them all (interval is 60K on 4.2 IIRC). Obviously look at plug 4 in any case diagnostically--oily? wet? fouled? burnt?...

2. Run Techron through a couple of cycles--either for injector or dirty valve type issues.

Mister Bally

If the repair manual search does not help, use the wiring diagram to follow the coil pack wires to the control module. There should be an index that describes or shows the module location. Recall my earlier post that mentioned the ecu under the plastic plenum. Keep in mind that ecu is secured with the Audi "chastity belt" and is a pita to remove. Also, quite pricey and requires dealer intervention to get a new one to work.

beachcomber

Thanks everyone for your suggestions. Apparently the 2008 D3 4.2 V8 doesn't have a separate ignition control module aka power output stage, but rather it is incorporated into each of the coils, which explains why I wasn't able to find it.

MP4.2+6.0

Correct. Those went away on at least larger Audi motors by later 90's as they moved to coil on plug fired directly by the ECU. Even my 2000 A6 4.2 was already there, while my 1996 A6 still had old style plug wires and a couple of ignition modules.

gbmarc

Beachcomber, were you ever able to solve your #4 misfire? I have exactly the same problem on cylinder #4
I've changed plugs, tried a new coil with no success and it's getting worse.