: idle speed control



TMO
05-11-08, 02:55 PM
I have a 99 Deville D'Elegance with 32K miles on a new GM crate northstar.
I recently have had problems with high idle speeds. (totaly random)
Anywhere from 950 to 2500 rpm's.
I took it to the dealership and they changed the throttle position sensor thinking it was sticking but it's not.
I unplugged what I thought to be the idle speed control (motor?)
So far the engine has not idled above700 RPM.
The part I unplugged is just above throttle position sensor.
Can't seem to find any info on this. I'm I correct in my thinking?

Ranger
05-11-08, 03:33 PM
What you unplugged is the IAC (Idle Air Control) valve. Your car does not have an ISC motor. Give the TB a good scrub down. If it continues, pull the IAC valve and clean it.

TMO
05-11-08, 04:22 PM
I pulled the air control valve and cleaned it with STP throttle body cleaner, hooked it back up and seems to be fine now. :thumbsup:

TMO
05-11-08, 04:25 PM
What you unplugged is the IAC (Idle Air Control) valve. Your car does not have an ISC motor. Give the TB a good scrub down. If it continues, pull the IAC valve and clean it.

Thanks alot, thats exactly what we did and seems to be OK. I priced the part at a local store for $60 but the $3 can of cleaner may have done it :)

TMO
05-12-08, 09:34 AM
JFYI
Wife took her rig to church and it did it again so it's unplugged again.
So I guess it's a bad part? bad signal? No codes.....

chubbyranger
05-12-08, 11:38 PM
:hmm: I would expect you'd have some codes with the IAC deliberately unplugged.

TMO
05-16-08, 01:55 PM
yes I have codes but haven't checked or cleared. Soon as I get the new part on I'll see what they are.
I have now noticed power loss and no trans kickdown when passing now that it's unplugged.