I have a recently purchased a 2004 A4 Quattro that is throwing up multiple error codes. The repair shop installed a new upstream O2 sensor and cleared the codes. The codes came back while I was driving to work after about half an hour of driving.
The idle is a little rough when first started but I do not experience any issues after it warms up.

The codes are:
P0300
P0302
P0303
P0304
P1111
P1136
P1479

After looking at other posts with similar codes I am leaning towards replacing the fuel filter since I don't know when it was last replaced.

Any other thoughts as to what could be causing the errors.

 

The po300 to 304 are misfire codes. Check your coils and spark plugs.

 

Thanks for the suggestion. I replaced the plugs and coil pack and that cleared the misfire codes.

The P1111 and P1136 remain and P0507 has now popped up.

After doing some more searching it looks like it may be the PCV valve causing the rest of the codes. I am also going to replace the fuel filter and check out the vacuum lines.

 

hey i just had multiple misfires in my 2003 a4......i changed the knock sensor and that got rid of the problem. make sure you check the spark plugs and the coils and anything else that you can think of first cuz its a real bitch to get down to that thing.