My 1998 2.8 Quatttro idle goes up and down when stopped at a light, orwhen the car is not movingWTF?? why does it do that?? its like as if the idling control is screwed?? please help, the car is 5spd

 

check for vacuum leaks in the pipes and clean the throttle body out

 

Clean out the idle air control valve as well - carbon build-up there can cause erratic idle.

 

check for leaks

 

I had the same problem.

The cause is likely a very dirty throttle body.

Clean out your throttle body, it should fix the problem for you. If not, post back with more info after its clean.

 

thanks guy, i'll give it a try tonight.

 

Maybe i'm stupid or something, but I try to track the throttle body on my 2.8..does it go behind the motor??...does anyone have a diagram of how it looks like??...I know wat a throttle body looks like, but I mean the location of it??? thanks

 

Just follow your intake piping from the airbox back - I believe it's back behind the engine and down a little. Not the most accessible part, but it's down there not too far out of reach. Just clean the heck out of it with throttle body cleaner and scrub with a toothbrush and shop towels until you get it clean.

You may find that when you start the car up after you're done and it's back together, that the car starts kind of hard and idles rough for a little bit. This is normal since the TB cleaner is mixing in the combustion chambers. It's designed to be combustible and will burn off, but it may take a few seconds (and be accompanied by black smoke out the exhaust). If you see/hear this, don't be concerned - it's normal. And I seriously think that as long as you're in there, clean some of your electrical connectors as well (mass air sensor mainly, but any of the others that are within reach as well - use electrical contact cleaner or (if you can find it) ProGold, which we use in aerospace). Doing that along with cleaning the throttle body will help a lot with smoothing things out. And as I said before, cleaning the idle air control system is not a bad idea either - everything that you can clean up and improve functioning on, will go a long way toward getting your car running smoothly and as it should.

 

I've checked all vacuum lines, and remove and cleaned the "living daylights" outta the throttle body, but no change...still idling funny....HELP!!!!

 

Is there a CEL on at all?