I have a 2000 S4 nothing new has been done to the car. Out of nowhere, the car lost power. I would guess that I'm down 50 to 70 HP from what I had before this problem. Then the yellow check engine light came on. I took it to our local dealer. The said it was the mass airflow sensor and replaced it, cleared the codes and told me it was fixed. I picked up the car and the car is still running like crap and the check engine light came back on. I've had other problems with this dealer so decided to take the car to a local performance European shop. They had the car for a day and said other than the codes everything checked out ok. The codes P1129 long term fuel trim, bank 2 rich and P1127 long-term fuel trim, bank 1 rich. They checked the fuel pressure and the o2 sensors they said they all checked out fine. Any idea what could be wrong with this thing?
Thanks all for any help!

 

if you are unmodded, then you have nothing to fear.

 

Is it completely stock? If the dealer cleared all the codes and those two codes came back, most likely the O2 sensors are bad. Maybe the MAF sensor. What you need to do is find someone with a VAG tool and log block 003 and 031. Your g/s at idle should not go lower than 2 g/s. If it goes below 2g/s the sensor might be going bad. Also do some 3rd gear WOT runs and log those two blocks. It could even be a bad hose on the intake or on the pressure side.

Mau

 

Have you checked your TBB? That is often a problem

 

You may even have a rip in one of the main intake hoses causing a mucho rich condition since a lot of the air is venting to atmos instead of going in the engine. Check that throttle body boot hose as Bob suggested...likely culprit

 

I don't have any factory warrantee left but I did purchase an extended warrantee $0 deductible 100,000-mile coverage. The car is modded a little it has a APR chip, Stebro cat back exhaust and a BMC Air Filter. Other than that, it's bone stock. The dealer I took it to said the MAF sensor was bad replaced it cleared the codes and said the car was done. I picked it up and it still ran like crap. After I drove the car for 10 to 15 miles, the Check Engine light came back on. The second shop I took it too had the car for a day called me and said they wanted me to pick it up and drive it because they couldn't find anything wrong other than the codes. They said the boots all looked good the O2 sensors all tested OK and they drove it and said it was running great! WTH am I nuts or what! I picked up the car paid the $180 bill and drove the car off, it had no power and after 10 to 15 miles, the check engine light came on again. I called them and they said to bring it back in as soon as possible. I told them that I really don't think I should be paying them $180 to not fix the problem. They said that the charge was for diagnostic time and the warrantee I have will not cover diagnostics just repairs. Anyhow, I'm taking it back to shop number 2 today to see what they can find wrong. I'll let you all know. To me it sounds like I have a bad waste gate. Maybe one or both are sticking. Does this sound like a possibility?

Thanks to all of you for your help!