2000 Audi S4. Every once in a while, if I leave my car idling for a few minutes, the car starts to shake sort of. But when I give it a little gas in neutral for a few seconds, or i put it in gear and drive for a short distance, it stops. Ive been having this issue for a couple weeks now. I have replaced the fuel filter just a couple days ago and its still doing it. At some points the car wont even start. It turns over fine, just doesnt start until I pump the pedal numerous times and then it slowly comes back to life. I have absolutely no idea what it could be now. i was almost sure the fuel filter would cause it but i was wrong. any help or ideas would be great guys. thanks alot

 

Could be the fuel pump or, kind of a long shot, the pressure regulator.

Are you getting a CEL or are any codes popping up? I don't think the pump has a sensor that would throw a code, so if there is none then I would start by looking there. I could be wrong about that though.

 

well yes the CEL is on but its on because I removed the electronic governor off the car. How hard is it to replace the fuel pump and where is it located? that might be the next part I replace to try and fix the issue

 

http://forums.audiworld.com/showthread.php?t=1480614

this is a good write up about how to take one out.

they are almost always on top of the fuel tank and accessable through the trunk.

i would also be skeptical of your MAF sensor, bad ones usually share the same symptoms of a rough idle, hard start ups, etc. if you haven't changed the stock one out, this would be a good first solution, seeing as they almost always go out on B5 S4's anyways.

 

Do the B5S4s have a ISV? (Idle stabilazation valve)?
something to check if so.

 

UPDATE........ Took my s4 in today and had it run through the computer. It turns out that valve 6 isnt firing. Its an on and off issue that is solved temporarily by pushing on the gas. Ive narrowed it down to a bad fuel injector in that valve. all in favor say "aye" haha. if not, what do you think?

 

it's just not firing or it's misfiring? if misfiring it could be a coilpack, switch one with another and see if that cylinder has the same problem