I have a 1999 A4 Avant. I purchased gas and did not put my gas cap back on. After a day, the engine started running rough. I bought a new gas cap to put on but it still runs rough. Does anyone know why?

 

I just bought a 2002 A4 QV6. I left the lot and filled it up and put in 87 out of habit. I should have read the gas cap!!!!! The I went 5 days later to fill up and put 94 in it. Ran much better but then i noticed the check engine light on (not blinking). Took it to the Audi joint i bout it from and they put the computer on it and said the code was that there was 'gas trapped' brobably because I did the 87 thing. They cleared the code and it did not resurface.

He told me that not closing the cap correctly or not replacing the cap gives the same code. I hope that helps

 

Get it vagged (read the codes) and tell us what comes up.

 

Take your car to a local auto parts palce and have them read the trouble codes. They should do this for free...

 

I went to autozone and they detected that it was a misfire in engine 3. I changed the spark plug and the ignition coil but the check engine light still flashes and the engine runs rough. Could someone advice what else?

 

Might be the ignition control module. Change the coils around and see if you're still misfiring.

 

it was the ignition control module. after changing it, it worked fine. thx