Hello all, 2008 A4 Quattro Turbo with 100k...

Been looking through the posts and do not see anything that exactly captures my problem. Initially was getting a P0303 code, for misfire in cyl 3. We took it in and had two coils replaced, then the trouble returned and this time new codes for two other cyls, so, all 4 coils were replaced and 4 new NKG plugs installed.

Initially, no issues, but check engine light has come back on, and feel a bit of hesitation. I want to gather as much info as possible before I return to the shop. Can anyone give me any advice about what else to check? We have not run the new code yet, but will shortly.

Thanks in advance for any info!

 

Possible that the PCV valve (or a related breather hose) no longer working to reduce the positive crankcase pressure. I just went through this on my 2007. This slowly got worse and I went from a misfire on one cyl to misfires on all 4.

You get hesitation when coming to a stop? Check your oil cap when the car is running. Is it hard to pull off? That is a telltale sign of leakage allowing air into the crankcase.
Before you go replacing the PCV valve though, check the o-ring on your dipstick to make sure it's sealed, as well as all the hoses related to the PCV system to check for cracks.

 

Yeah, it seems I was able to clear the misfire with all the coils and plugs. I still get an "Underboost" code. I think it is 0299, but I do not have my scrap of paper with the number in front of me. Going to try a few things and then pull the diverter valve to see if that is the issue.