I have an '03 Evo VIII with around 86k on it. My idle went to crap and my car kept dying at stops so I checked out the IAC and found the teeth worn down so I replaced it. The new IAC didn't have teeth on it and had the spring on the outside. From what I have read it should be interchangeable.
It fixed the dying at stoplight issue but my car now idles at 2500 - 3000 rpm at a stoplight.
I have checked the o-ring on the IAC and the vacuum lines. They all seem fine but I will build a tester tomorrow for a leak test.
Please Help!!!

 

Anyone?

 

There was a previous post about something similar.

Try disconnecting the battery for a few seconds. It needs to relearn the idle.

 

I tried this a few times before with no success but I tried the reset again today and the car perfect now. Not sure what is different but I appreciate the response.

 

x2

But if that doesn't work:
Also is your idle at stop bouncing around 3k constantly? Try unplugging the control valve and see if there is any difference in idle. I recently put an evo 8 ICV in my IX and had weird issues were it was getting stuck in open position (rpm bouncing at around 3k).

 

Just curious, I know this is an old thread.. but if the idle is staying high, and you unplug the IAC with no change in idle does that mean the IAC is sticking open?

 

It just means it is unplugged and not working (if it was before) - not a test for anything I know of.

 

The best thing to do is pull the IAC off the TB, then observe movement (or not) when keying the ignition. Clearly don't try to start the car, but just powered the ECU will make it move.

I fixed my issues by blasting out the IAC by-pass passages with carb cleaner.

 

I had a similar issue. The IAC stuck full open. It fixed itself after a couple cycles of the key.