Like the title say when idling, the check engine light will flash, and it runs rough. When I give it gas it goes away. I get the bank 1 & 2 lean, and misfire on all 8 cyl. I changed the maf sensor with no help, changed plugs. I do not believe that it is coil packs, because it seams to run fine when giving gas. I am planning on checking vacuum lines today. Anything anyones got, let me know. I have been fighting this problem for a week now and am getting tired of it. This is my 3rd A6 4.2L, and is the worst one by far.

 

No one has ever had this problem, I am assuming. I checked vacuum lines and found nothing. Still same codes misfire on all 8 cyl, and lean bank 1&2.
I am open to any Ideas.

 

It's a car that I'm interested in buying that has this same problem. I haven't bought it yet, their still looking for the title... But I did run a diagnostic check, the handheld code scanner pulled up misfire on cyl 3 and 7. At idle you can feel the engine rock lightly with the misfiring, you can also smell the unburned gas fumes in the exhaust after a cold start because the cats are still cold. The problem goes away with a press of the accelerator peddle, and the engine smooths out.
The guy Im buying it from said he's had the car just 2 years without doing any tuneups, so going by what he said I was thinning it was a simple fix with a major tuneup and plugs... We'll after reading your post Im thinking maybe not now.. Did you resolve the problem?

Thanks,
Doug

 

Well, I bought the car. Ew! Why would they put Motorcraft plugs in a Euro car? Anywasy, Yeah, I pulled the plugs and on cyl 3 and 7, the plugs are wet and smell of gas. The gaps were way too wide and I took them down to .032. Later today Im going to try and move the coil packs over on a different calender and see if the problem moved to the new placement. But it was another post where someone mentioned in a reply comment about checking the ECM and its two modules somewhere inside the engine compartment, on the air box I believe they said. But too the issue they had was a shutter on acceleration so that may not be a good lead for this issue.

 

Have you checked the battery's voltage both while resting and while the car is running? I recently had random misfires on my M6 (All 10 cylinders were producing random misfires) and it was actually a battery that was wreaking havoc with the ignition system. If you've ruled out a vacuum issue, I would then start to look for fuel delivery being an issue. After that potentially a timing issue, but I would think it would throw other codes as well for retarded/advanced timing.

Those issues with banks 1 and 2 being lean are almost certainly related to the ignition issue.

 

I found the culprit just today, I would always get misfire on cyl 3 and 7. I took those coils and moved them over to 2, and 6, and wah lah! The trouble codes fallowed to where I had moved the coils. I just ordered used genuine Audi coils from a eBay salvage seller for 10 bucks each. I got two good tested oem units for less then the price for one new generic and the local auto parts store.