So I bought a 1996 Audi A4 from craigslist. 125,xxx miles on it.

The car has a custom air intake which the previous owner said he installed himself and then the car started to act up on him. The problem seems to be when the car is in idle. The RPM's bounce from around 1200 down to about 700 and back up again and there is some serious vibration, especially when starting the car up. Driving the car however, it is completely smooth and you wouldn't know the difference.

The shady part is while trying to get ahold of the owner again to ask him about it, he cut off all communication to me, not answering his phone and simply sending me a text saying that it's not his problem anymore and not to contact him. Before this he mentioned that he threw the original intake away. On top of that, little known to me when I purchased the car, he went in the dash and disconnected the check engine light so now upon staring under my steering wheel I can see a yellow light blinking which I can only suspect to be the check engine light.

Now I took off the air filter and cleaned the air mass sensor from inside with some cleaner and the car responded to that at first, but the effects wore off and the vibration returned. Could this be that the air mass sensor is faulty or is it likely that it is just the air intake he installed?

Any opinions would be appropriated and Happy Holidays to everyone out there!

 

Sorry to hear about your troubles. You could be correct with the MAF being bad even after you cleaned it. Also what kind filter is it? K&N or some other type of pre-oiled filter? Try to was the filter and see if that makes a difference. If not, a new MAF may be in order.

 

It is not K&N. I am not sure what type it is but the filter itself doesn't seem relatively dirty. Do you still advise that being the first part to replace?

Also, do you know which fault code reader will work for the 1996 Audi A4. If memory serves me correct there are 3 or 4 different types of fault code readers.

Thanks.

 

Fixed check engine light which had been disconnected. Got fault codes P300, P301, P302 & P303.

Where should I start?

 

Those are misfire codes. 300 is a general misfire, and 301 correlates to cylinder 1, 302 to cylinder 2, 303 to cylinder 3. Check the spark plugs (or just change all of them - it's cheap and easy), and see what happens. It could be the coil packs going although it's usually the 1.8T guys that seem to have that issue. You might try a Seafoam treatment first, then change plugs, and see how it runs from there.

 

Replaced coils and plugs Wednesday.
No luck.

Thursday I seafoamed.
No luck.

Spent all of yesterday checking vacuum lines but finding a lot of them either have no suction or pressure. Was thinking it was the solenoids but couldn't find much reference here on the boards.