bryce dube

I have a 2004 Audi A4 3.0 V6 I can't seem to find out what my problem is. I have three misfire codes cyldiner 1 2 and 3 (bank 1) a random misfire code and p0431 which is warmup catalyst below efficiency (bank 2) ....any ideas???

turbo510

Often problems on one bank result from valve timing issues, so do you know that the last belt service was done properly (with the correct tools and procedures)? Not likely that plugs or injectors are marginal on one side only, but perhaps a plug change and Techron fuel system treatment through a tank of gas might help.

lyleswk

If it were a 1.8T, I would point to vacuum leak, but don't know if the 3.0 is as susceptible to vacuum driven issues...