View Full Version : 1994 sts Idles @ 2-3 thousand RPM

01-01-05, 07:42 PM
Car fluxtuates between 2-3 Thousand RPM mostly above 2500 .Has anyone else had this problem.Or Is there someone who has enough of a background with fuel meatering on this generation engine it's the V8.I read the other posts in regaurd to Idle problems. Throttle body seems to be working fine.ICS from looking at it doesn't seem to be holding throttle body valve open is this a purely mechanical componet? If I restrict air flow idle will come down to about 1000-1200.I looked everywhere for vacume leaks couldn't find any.TPS?
Any help would greatly be appreciated Thanks Philip

01-01-05, 09:20 PM
Part of the puzzle here is whether this is something that just happened or has been a long standing problems since you bought the car.... It makes a difference as to what would be the first thing to look for.

It sounds like the idle speed control motor is failing/failed.....or there is a severe vacuum leak somewhere.

Look at the idle speed control motor (the canister with the plunger on the end) and see if the plunger of the ISC motor is touching the throttle lever. If so, then it is holding the throttle open. If not, then something else is holding the throttle open.

Disconnect the cruise control link to the throttle lever at the cruise control diaphragm to make sure the cruise link is not holding the throttle open.

Turn the key on and off while watching the idle speed control motor to see if it moves at all and/or responds when the key is turned on and then turned off without starting the engine.

If the idle speed control motor is not moving then it is likely failed and will need to be replaced.

If it moves then depress the plunger of the ISC motor while the engine is idling fast and it should retract. Keep depressing the plunger to keep the ISC motor plunger retracting until it is fully retracted and stops. Disconnect the wire connector to the ISC motor to "freeze" it. Close the throttle and check for clearance between the ISC plunger and the throttle lever and check the idle speed. It should be around 450-500 RPM when there is clearance betweent the plunger and the throttle lever with the throttle in the closed position.

If the ISC motor will not move you need to unbolt it or disconnect the bracket from the throttle body and see where the engine is idling with the idle speed control motor out of the picture.

This isn't a fuel metering or spark problem...nor likely to be a TPS problem initially. Something is letting too much air into the engine so as to make the idle too fast. Either it is the idle speed control motor or something holding the throttle open so the idle speed control motor cannot close the throttle sufficiently.

If you search the forum using "idle speed control" or "ISC motor" or "closed throttle switch" there is quite a bit of info available...

01-02-05, 11:21 AM
Thanks so much for your help I really appreciate the quick replay.I wlill go out today and determine the problem again ThanK you . Philip