First time poster, interested in the educated opinions of the crowd here.

I have an '06 A3 with close to 95K miles. The car ran beautifully for the first 6 years/70k miles, then began throwing misfire codes that seem to plague so many owners. This coincided with the end of my complimentary dealer maintenance so I took the car to my independent mechanic.

Through them, we tried the typical troubleshooting of swapping coils to see if the code followed the coil which it did so we ended up replacing coils and plugs. Reset the code until CEL came back on....same codes, plus another for the turbo pressure sensor (I think that was it -- not looking at paperwork at the moment to verify part) which we ended up replacing and reset the codes. Continued driving until CEL came on again with same misfire codes plus anoghte for turbo cut-off valve (again, think that was the part). Continued driving and CEL came back with same misfire codes. More coil chasing ensued. (At around this time I took a job that put me on the road 100 miles per day, thus rapidly putting more miles on the car. Within three months of the new job, I noticed substantial a power hit when downshifting or trying to get RPM's above 3500. It was obvious that problem was getting worse.) Went to the internet where I read on this forum and others about misfires, camshaft follower warranty extension, and other persistent problems with carbon buildup. With new info about camshaft warranty in hand, I brought my car to the Audi dealer who replaced the follower for free. CEL went away for about 2 months and then came back with same damn misfire codes. Brought the car back to the dealer who did another inspection. I expected them to tell me that there was carbon buildup, and in fact when the service tech called me to tell me that he was keeping the car for an extra day he speculated that it was carbon buildup. The next day however, I received a call from the dealer who said that it wasn't carbon buildup but that my catalytic converter was breaking down. (Which is very painful because I've been chasing this problem now for 2 years and 25k miles, I am now over the federal warranty of 80k miles for catalytic converters and looking at $2000 for parts-n-labor.)

What concerns me is that, as I see it, one of two things has been happening the entire time.
A) The catalytic converter started failing 25k miles ago and has been throwing incorrect misfire codes the entire time, thus causing us to "fix" the wrong problem up to this point.

or

B) There is still an unidentified problem within the fuel system as a whole that leads to carbon buildup and/or misfires, which in turn leads to unburnt fuel entering the cat and thus deteriorating it over time. In which case, even if we change the cat, we still haven't solved the root cause the problem.

Either way, it seems that Audi should be responsible for the cat change since their computer has never properly identified the root of the problem.

Wondering if anyone else can weigh in on what may be the root cause of the problem, and/or if you've had this cat-n-mouse game, and/or if you've taken it to Audi of America and/or what other ideas you might have.

Thanks in advance

 

I am having the same issue, changed coil packs and plugs. The dealer told me that I may need new injectors. From my research it looks like it may be a problem in the computer itself. I get great gas mileage, but my power dies when I run it hard (boosting). Dealer wants $1100 for a 'carbon clean out.' LMAO

 

My 06 A3 90,000 miles is having a similar problem. Engine light comes on and there is mid-fire on #4 (I think) - but only when cold (California cold). Swapped coil/new plugs. No change. Dealer recommended trying a gas additive which I have done 3x. Been OK last week or so, so perhaps that helped.

I have heard there is a place the will "refurbish" all 4 injectors for $100 - you UPS it to them. Don't know if that's just cleaning them or what.

Jim

 

Also, I have replaced my Cat Converter a year or two ago as it got damaged an rattled. Went to my local (great) muffler shop and they did it for, I think, ~$900 and I think that was Audi parts.