I just recently installed heads and replaced my IAC because the old one I was lead to believe was bad because my idle would pulse up and down until the motor was warm. But now the car will start and turn off or barley start then rpm pulse and it dies. I unplug the IAC and it will start perfect. Sometimes after driving for a bit and I go to neutral sometimes it will idle at 1800 rpm for about 10-20 seconds then rpm pulse or just goto normal idle? Everything kinda happens randomly could this be needing a new tune or my IAC? I ask because I went from 241 heads to 243, I already had it tuned awhile back with bolt ons and cam.

 

Id say it needs a tune.

 

I had heard something about somebody who had installed the IAC backwards and it caused an issue like that. Maybe I'm thinking of something else.

Something to check anyway.

 

Ya I am pretty sure its on the right way. Thanks for the suggestion.

 

I would post this in the tuning section because I think it could be a tuning issue...

 

^tried not one reply?

 

when you say RPM "pulse" do you mean its searching for idle? or is it more like the idle is hanging?

 

if you only switched heads, nothing else, and it did not do this before the swap, I would bet against it being tune related. Are you sure you got the grounds that tighten down to the back side of your driver's side head are secured, clean, etc?