Help! Hanging idel

[Marv02]

The motor runs great but the Idel has always done this even when the car was stock.

When comming to a stop or getting off the gas to Idel hangs about 1000 to 1200 RPM's for a minute or 2 before drops down to the set idel of 750 RPM is this normal.

I set the base idel when motor hot set the TPS, reset the ACV, and timming each time it works out great but when drive the car the idel still hangs.


Anyone know why and how to fix this.

 

[boomdriver]

I'd guess the cable is hanging.
After the ECM goes closed loop....and the IAC take idle control, it should always sit around 600-700 in gear warm. When the a/c comes on the IAC should bump the idle 50 rpm...and let it drop if the a/c compressor cycles off. If the IAC is working right, the idle stays the same when the compressor turns on/off.

The throttle cables have a liner inside thats hard plastic and wears out. That breaks inside the sleeve and a broken wire strand will hang on the end of the sleeve and not let it go all the way to full return/idle. The throttle should be 100% closed, at idle with NO idle screw holding it open any. The IAC should be doing that, not the adjusting screw. Back off of that to make sure.

 

[aklim]

I think the ECM is commanding a different idle than what the FSM says to set it at

 

[G Winter]

Check the throttle shaft for forward , aft play with engine off. I have this problem, getting worse.
The play causes the plates to bind. Does it drop almost immediately if you burp the throttle?
I am in search of a throttle body for my 90 to use while I repair the throttle shaft bore on mine.




Glenn