85 that hunts at idle

[Ruby Fan]

85 with 75K miles runs great 23 mpg. But it seems to 'hunt' for a smooth idle. It doesn't stall, just that the idle isn't regular smooth. Is there some kind of emission valve that is worn/used out? thanks

 

[Badgerfan79]

I just had this issue with my 86, after installing a FIRST intake, runners, plenum, throttle body, and bigger injectors. I thought maybe I had a vacuum leak or other major issue, but it turned out to the the IAC valve. It's installed in the throttle body. $60 part and it was a bit of a pain to replace in my setup but I think it's pretty easy to remove on a stock engine. I can't say for sure if that's your problem but it fixed mine. If you can get it on a computer you want to see the "IAC position" reading. Mine read "160" constantly, which means it was stuck open. Hope that helps.