Occasionally at startup my 87 renix 4.0L idles high at startup and will not kick down. Shut off and restart the motor and it idles correctly. First noticed this high idle when I adjusted the automatic trans. cable adjuster on the throttle, it idled real high, and then I readjusted and it seemed normal again. Since then occasionally starts with fast idle, and idles fast when driving. I am not sure if the auto trans. cable adjuster is working correctly. Or maybe I am adjusting it wrong, followed manual best I could on the adjusting.
Anyone had any experience with this problem?

 

replace the idle control motor.

 

Do you mean the idle speed stepper motor, according to the Haynes manual?
Do you know if it can be cleaned or tested, etc?

 

I have had a hell of a time tracking down my idle issue. My idle issue was similar to yours, in that it would idle up to 1500 at random, I'd shut it down and restart, then it would go back to normal for a bit. I adjusted the set screw for the throttle stop, adjusted TPS, cleaned IAC motor, cleaned throttle body, and finally after fidgeting with all of those at the same time to find the right combo, the high idle went away. That was only after replacing the EGR, TPS, IAC, MAP, and trying all of the aforementioned separately. My problem now, is an inconsistent idle. It varies between 500-1000, and I can't put my finger on it. Have you had any luck since this last post?

 

In the tech forum I found this link to Renix idle problems it is real long but full of good info from others battling the same idle issues.
http://www.naxja.org/forum/showthread.php?t=905849

I have cleaned engine grounds, checked TPS settings, cleaned TB & idle speed stepper motor, but mine is still has a fast idle. It seems like it is getting worse, I think I may have a vacuum leak, I am going to have to do some serious vacuum leak testing.