when i got my hatch the car idled perfectly but then it started to run rich because of the ecu it had the wrong one so i switched out the ecu and the car started an ran like it would normally the only problem was that the car wouldnt idle it go from 1k-2k and keep going back up and down and it really gets annoying but im not sure what it is some one told me it was the idle control valve but if that is what it was then it would of done the same thing when the old ecu was in. so i was wondering if anyone had any idea what it is.

 

try the search button. There are lots of threads out about this right now...

 

if a car has an idle surge, but the ecu is making it run extremely rich it will often prevent it from surging by bogging down the engine. Maybe it wasn't surging with the old ecu due to the richness.

 

Check for vacuum leaks. My car used to do that and it was a vacuum leak.

 

sounds like my car, does it stop after you drive the car after a while?

 

no it still does it, wen i first turn on the car its good but wen i start moving it starts

 

First check for vacume leaks. If none are found then remove IAC and clean it. Then clean your throtle body and air bypass screw would recomend removing it as carbon will build up inside the ports, clean that also. If you have a thermal fast idle valve check to see if it is still in adjustment, if not then adjust it. Then check your TPS voltage and make sure it is in spec, if not adjust it. then check you base timing. Also make sure your coolent system does not have any air pockets and topped of properly. After checking thses items and problem is still not solved let us know.

 

bad gas/o2 sensor

 

NO LISTEN TO THIS GUY HE JUST TOLD U EVERYTHING THAT U NEED TO KNOW ON HOW TO TRACK DOWN THIS PROBLEM

 

IAC! Change it out...