Need diagnostic help - Cold start misfires

[xstwin]

Background:
2011 A4 w/ APR stage 2 (turbo back exhaust & test-pipe since new). 97K on the clock. Dealer maintained for regular service.

Issue:
Regardless of outside temps, cold starts cause a misfire. I can hear it and feel it in the engine vibration. Goes away after rpm drop to regular idle and car either sits or is driven. No other issues and does not reappear on warm/hot starts.

Codes:
300, 301, 304, etc. (random misfires, misfire cylinder 4...)
Cylinder 4 seems to be the one that pops up most often, but codes for all 4 cylinders do pop up.

Replaced the coil packs & plugs for all 4 cylinders. Replaced the PCV unit (not hoses, they appear to be ok but haven't tested).

Stumped!!! Anyone have guidance on what next?
Thanks.
B.

[Abu_boost]

Background:
2011 A4 w/ APR stage 2 (turbo back exhaust & test-pipe since new). 97K on the clock. Dealer maintained for regular service.

Issue:
Regardless of outside temps, cold starts cause a misfire. I can hear it and feel it in the engine vibration. Goes away after rpm drop to regular idle and car either sits or is driven. No other issues and does not reappear on warm/hot starts.

Codes:
300, 301, 304, etc. (random misfires, misfire cylinder 4...)
Cylinder 4 seems to be the one that pops up most often, but codes for all 4 cylinders do pop up.

Replaced the coil packs & plugs for all 4 cylinders. Replaced the PCV unit (not hoses, they appear to be ok but haven't tested).

Stumped!!! Anyone have guidance on what next?
Thanks.
B.

ooo boy.. read my thread

http://www.audizine.com/forum/showth...-Misfire-Issue

[kdaffy]

my initial reaction would be carbon buildup - mine did this and it went away after the carbon cleaning...

[Abu_boost]

I agree.. start looking at the basics first.. injectors, carbon cleaning, compression test..

[xstwin]

I take the suggestion of injectors/ carbon, but don't believe its compression related as I don't have issues after 30 sec of warmup. Unless you're saying that a cold compression test on Cyl 4 compared to hot compression when all is fine. That would suggest carbon on valves and not sealing. It doesn't sound like fuel blow by into the exhaust during misfire, more like an spark or injector not firing. Injector/spark is weird cause why would that be on cold only.

Hmmm

[Fburg A4]

Did you check the misfire counter and actually see the number of misfires occurring on each cylinder? That may help narrow it down if one bad cylinder is missing enough to set codes for other cylinders.
I will throw out a bad scenario of a cold start misfire, head gasket leaking coolant into a cylinder after you turn the car off

[Abu_boost]

Did you check the misfire counter and actually see the number of misfires occurring on each cylinder? That may help narrow it down if one bad cylinder is missing enough to set codes for other cylinders.
I will throw out a bad scenario of a cold start misfire, head gasket leaking coolant into a cylinder after you turn the car off

I just got my vagcom.. but how do I check the misfire count.

[Fburg A4]

It is in the engine control. I think it says misfires per 1000 Rev or something like that. Just go into the engine controller and look at the advanced measurement blocks and look for misfires. They have one for each cylinder. It would be a good idea to get that set up before you cold start the car so you can see the count as the engine stumbles