recently my car's idle has been flucuating up and down. This same thing happened a year or year and a half ago and i brought it to a shop and they "replaced" the IAC. Now i am not sure if my CAI system has something to do with this or if maybe i got scammed when i brought it to this shop and maybe they just cleaned it off with some Brake clean instead of replacing it or something. But what i am wondering is if there are any other things people ran into with this problem. I don't want to spend the money on an IAC and have it not truely be the problem.

 

There can be a couple of causes for idle fluctuation. True the IAC valve could be the culprit - you could unplug it while the engine is running and see if the fluctuation changes... the other possibilities are a vacuum leak - older Accords were prone to intake gasket leakage. Probably the most common cause is low coolant level. If this is the case, the idle will be ok when the engine is cold, but get worse as it warms up. There is coolant running through the IAC and I think (not sure) there might be a fast idle valve. If your coolant level is low, or you have an air pocket in one of these areas it can cause a "rolling" idle.... up and down and up and down.....

 

yes, i have fixed many a erratic idle by fixing the fitv. there is a good diy fix post on the fitv (fast idle thermovalve) on the EF forums....basically it has two coolant lines going to it... it will have a plate with two phillips screws holding it on, remove those and there is a large retainer that is threaded inside it loosens up and causes a fluctuating idle...search for the thread as it has pictures, etc...ill see if i can find it...

 

this thread has some good pictures of what i am talking about...

https://honda-tech.com/zerothread?id=1097981