SpotlightR

Good day all,

I have a 2008 A6 4.2, 156k miles, timing chain/tensioner service done 10k miles ago. For about half a year now the car has been misfiring on cold start, though the misfire is far less noticeable when the outside temperature is warm. I live in Texas so our winter was not too bad. The misfire clears up for the most part after the engine revs over ~3k rpm, though sometimes when I'm idling when the engine is at any temperature I think that I feel a slight misfire. Also, when i am in Drive but not Sport, if I accelerate and then let off the gas, the RPMs will drop significantly then shoot back up, when I'm in Sport the RPMs stay high and they don't fall after accelerating. Any ideas? It doesn't bother me too much but I'm at a loss. Thanks.

dzywicki

I was chasing a cold misfire problem on my 08 A6 4.2 for awhile. It was new to me and I suspect that's why the PO wanted to get rid of it. My first check was plugs. I replaced those. When I replaced them. I noticed oil in several of the spark plug wells. I replaced the valve cover gaskets and the oil went away and the cold misfires went away. Then they came back. I started checking coils to see if it moved and finally figured out it was the coil connectors. The plastic connectors had the locking piece broken off at some point so the coil connectors were being held in place by just the screws to the valve cover. I could press them tight and the problem would be gone until I hit a bump or something else that seemed to make it move a tiny bit. I just ordered replacement coil connectors and will hopefully get those on this weekend and then I think my overall misfire problem will be gone.
For the cold misfire, I suspect that the oil was leaking past the valve cover gasket when cold, but would swell just enough as it warmed up that the oil would stop coming in.

SpotlightR

Absolutely spot on. Took coils out of bank 2, found oil. Thank you so much!

dzywicki

Valve cover gasket replacement is pretty simple. I ordered a beck-arnley replacement through amazon and had to modify the drivers side a bit. Seems to be a common problem. I haven't had any oil in the spark plug tubes since replacing those.