I have an 99a4 avant 2.8 and i have not had a problem in the 6 months i have owned it. I was installing my subwoofer today and caused some damage nd autozone is closed tonite so i cant say the diagnostic. I disconnected the battery and i installed the amp when i hooked everything back up and turned it on, the engine was lacking serious power and fluxuating like crazy.my subwoofer amp went out but i checked all fuses on the car and stereo and nothing blew out. Started car backup, wouldnt hold idle and dies and checkengine light on. It chokes and bounces up and down at 1500 rpm andstruggles idling at 3-400 rpm then dies. It tops out at 40 mph and wont shift when i rev.catalytic converter? fuel pump? O2 sensor ?
Can someone please help me out before i break my wallet at the auto shop ? any suggestions
thanks

 

You need to try and limp it to an AutoZone and get the scan done first -the codes will be a big help in diagnosing the problem.

 

Did you by any chance connected amp to your ecu instead of battery?