i have the rough idle problem whenever my car is stopped. it's been like that for about a month and i have absolutely no check engine light or any other lights on. it ONLY happens when im stopped at a light or w/e and when im backing up. i dont think its the o2 sensor, if it was... the CEL would of come on, right?

is there a way for me to check if its the Idle Air Control Valve? can it be anything else? will having a CAI play a role in this?

 

Odds are it's a dirty or bad IAC valve. Does it clear itself up every now and then? I've been waiting for some good instructions on how to clean the IAC valve, because I have an intermittent surging idle speed, and I'd like to try to clean it myself.

 

IAC, TPS, bad plugs, bad fuel pressure... could be many things that might not always give a CEL. However, it is possible you have an intermitten problem which throws a code, but not the CEL.

 

yea, it doesnt happen ALL the time... i would say 50/50.

 

cool, i guess i'll take it to discount auto parts and have them hook up the scanner and see if i have any codes.

do you know of any other places that do this for free?

 

IAC. Common problem on our cars. 95% probability. And it won't necessarily give a code or CEL.

Whoah, DAP? Don't let any morons touch your car!

 

If the IAC has gone bad, there are two states:

(i) It is stuck open... idle will be higher during cold-start or hot engine, won't be rough
(ii) It is stuck closed... idle will be rough during cold-start... but normal when hot.

 

Why are you doubting that it's the IAC valve?
If it is dirty and sticking intermittently, then it won't operate smoothly, and as the valve jumps around between its two extreme positions, the idle speed surges up and down. It's not completely stuck in one position...

 

can your car die at a stoplight or reversing if the IAC has gone bad because sometimes my car dies on me when It reverse or stop a stoplight and it starts right back up and seems fine like nothing happen and I never get a code so I cant figure out the problem

 

try resetting your ECU

 

I had ths problem & replaced my IAC valve at my cost, & it made no difference.

Dealer adjusted the valves again after a compression test told them they were off. So far after 2 weeks the car has been fine.