I just finished up my JDM H22 swap and turned the key on friday. It ran smooth as butter untill the engine warmed up. When it was up to operating temp the idle started to rev between 900-1200 rpm. I figured that i had a bad IACV because my old H23 did the same thing untill I had it fixed. My engine has no check engine lights on. What could the problem be?

 

This happened to me on a couple of occasions. When it warms up do the rad hoses feel like they are under pressure?
If there is a pocket of air trapped in front of the thermostat it wont open and cause an irregular idle.

 

air bubbles, vaccuum leak, iacv, fitv