high idle 2000rpm

jfields1977

New Member
Jan 12, 2007
3
0
0
I have a 1990 5.0 manual trans. When I start the car it idles at 2000 rpm and stays there. I have noticed over the past few weeks that at a stoplight the car would stay idling fast then drop to normal. I have replaced almost everything on this motor and am stuck. I recently replaced the IAC as I was told this was for sure the problem. I have no manifold vacuume leaks the IAC is new, MAS is working, TPS is calibrated and working. Doesn't seem to be a clutch issue. I adjusted the idle screw on the throttle body and brought the rpm down for a minute but when I restart the car it is hard to start and idle creeps back up to 2000. please help as this is my daily driver.
 
With a hot engine, what happens if the IAC electrical connector is disconnected? What RPM does it idle at?

Though you said you checked everything, it still sounds like a manifold vac leak.

Also, for ideas and tips (though not directly related, a lot of the tutorials would apply), see Jrichker's idle surge sticky.

Good luck.
 
You guys with idle problems could same a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first post has all the fixes, and steps through the how to find and fix you idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.