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View Full Version : IAC issues...Need experience from other SC'ers



phils89sc
10-07-2010, 07:36 AM
I just got the head gasket job finished on my 89SC and got her back up and running. She runs well, although at the moment, I have the SC bypassed because I need to replace the seal and pulley.

My problem is this and has been this since I got the car. When I start it, cold, there is no high idle. the RPM will rise to about 1100rpm and then back down to the normal 800 or so. It is a smooth idle. However, after the car warms up, I can start it and the RPM will jump up to about 1600 to 1800 rpm or so then come back down after about 3 to 5 seconds back to normal.

I have checked everywhere for vacuum leaks, resealed the IC piping, etc. I cannot figure out what the problem is, if there even is one?

For those who have 89 SC's, what does your car do when you start it cold and hot? I have tried 3 different IAC's, pretty much with the same result.

Is there a way to set the base idle on the SC?

Thanks for your help.

Pablo94SC
10-07-2010, 01:47 PM
Look for a FAQ from Fred4pt3 on setting the idle. It'll have you set the throttle blade and bleed screw so the car will idle without the IAC plugged in, then you can adjust as needed to bring the idle back down a bit.

TbirdSCFan
10-07-2010, 04:04 PM
Look for a FAQ from Fred4pt3 on setting the idle. It'll have you set the throttle blade and bleed screw so the car will idle without the IAC plugged in, then you can adjust as needed to bring the idle back down a bit.
Actually you don't want it to idle w/o the IAC plugged in. You want it to stall or cough and sputter like its going to stall. Just be sure that the throttle plate is lightly but fully closed with the engine off. You don't want any air gap.. thats the job of the IAC. If you have an air gap, that will create problems as the EEC will be confused at why the idle won't come down. :cool: All of this of course assumes your using the stock cam.