Sounds like a sticking valve. Might be a broken valve spring. Have you done a compression check?

Bob

 

Nope, haven't done a compression check. would a sticking valve cause codes p0300 and p0304. wouldn't that just throw a code on the cylinder that is sticking??

 

Did you check your catalytic converter? Now I really think it is exhaust back pressure related.

 

How do I check the catalytic converter???
All bentley talks about for my codes is fuel and ignition? Is there an area in the manual for checking the CAT?

 

Post #6

 

I have done everything in post 6 except the vacuum gauge. where is that supposed to connect? I haven't tried the 02 sensor removal yet either. that will be next. I think the indie shop was just trying to rob me originally cause after I went to them the dealer said the CATS were fine. And everything was good for awhile. Guess I'll try the 02 sensor thing next.
thanks fellas

 

To be honest with you, I guess I never even looked at any vacuum lines on my A6. My previous cars had little screws on intake manifold than unscrewed to hook a vacuum gauge. I guess you can tap into any vacuum lines as well. Anyways, let me go look and see if I can find a location to tap in. Also I would imagine it is shown in Bently under vacuum lines.

 

Hey guys i seem to have the same problem, after replacing thermostat, timing belt and water pump on my 2000 a6 2.7t the check ingine light came on a couple days later and my idle was weird right off the bat, i took the car back to the mechanic and i could not find anything but he felt the diffrence too, he checked the car's computer and it came back with bank 1 cat problem, he said that it needs to be replace but i just don't think that's the problem. any clues. BTW my car has 92000 miles