2001 Mustang GT idle problem

wvstar · 02-26-2007

The idle speed on my car yesterday just changed all of a sudden on a drive back from town.

I have just had the car about a month. It has always been rather cold natured on startup (have to feather throttle for about 30 seconds to keep her running first thing in the morning). After normal temps, the car has always idled around 800~ rpm. Sometimes, it would seem that it would idle around 1100 - 1200 briefly after stopping at a light, etc and then drop down to 800 in a few seconds.

Ever since yesterday, it wants to idle around 1500 rpm and then will drop down (same scenario as above) to only around 1100~ rpm.

I checked the linkage at the TB and everything seems to be free and clean. The idle set screw for the linkage seems to have a touch of blue loctite on it so I don't think it has changed position. I could adjust it to slow the idle down...but something else had to change to cause this.

Any ideas what to check? The car does also have a K&N filter but (as I said) I've had the car for about a month and it always ran the same until yesterday.

Any help appreciated!

Ron

reivaxtorres · 02-26-2007

take off the IAC and clean it with brake cleaner or carb cleaner. after driving on the freeway or around the streets, the rpms wouldnt drop to idle for awhile, and after a few minutes of this the rpms would drop to where they are supposed to be. after getting tired of this senario, i took off the IAC, cleaned it, re-installed it and it hasnt given me problems in awhile. just a thought tho.

wvstar · 02-27-2007

Thanks - if I can figure out what part actually is the IAC (idle adjustment controller) I'll try cleaning it. I found some past posts of similiar issues with idle and someone mentioned the Mass air flow sensor. I may try cleaning that with some electrical cleaner and see if it helps too.

If not...I'll just get my pocketbook ready and head for the Ford garage!

Thanks again!

reivaxtorres · 02-27-2007

haha, sorry, i should have been a little more specific. its the IAC is what is bolted on to the front of the intake plenum, has a rubber hose coming in from the intake, and has an electrical plug. here, take a look at the picture in this link:
http://www.pats-world.com/brightblue...c%20valve4.jpg

wvstar · 03-01-2007

Thank you kind sir! Turns out it was a bad IAC vlv. Had the Ford dealership replace it. They also cleaned my injectors and installed a new fuel filter. Cost me an arm and a leg but she seems to be running normal again. My car has a colder thermostat installed so they said it will want to run on a faster idle a little longer than if it had a normal temp installed.

Thanks for your tips. I need to get a manual for my Mustang and start studying up on it. I don't work on my cars much anymore myself, but I should and would like to get more familiar with the Ford. I've been a GM guy for most of my life (Camaros and TransAms)...but don't hold that against me! LOL

Ron

mbhmustang1998 · 03-03-2007

Quote:

Originally Posted by wvstar

Thank you kind sir! Turns out it was a bad IAC vlv. Had the Ford dealership replace it. They also cleaned my injectors and installed a new fuel filter. Cost me an arm and a leg but she seems to be running normal again. My car has a colder thermostat installed so they said it will want to run on a faster idle a little longer than if it had a normal temp installed.

Thanks for your tips. I need to get a manual for my Mustang and start studying up on it. I don't work on my cars much anymore myself, but I should and would like to get more familiar with the Ford. I've been a GM guy for most of my life (Camaros and TransAms)...but don't hold that against me! LOL

Ron

Glad you got it fixed. If only u had read the sticky at the top of this forum, u could have spent 50 bucks and changed the IAC yourself, I know u said u dont work on cars anymore but its 2 bolts and like 3 minutes. But oh well, glad u got her going pro

perly.

reivaxtorres · 03-03-2007

yup, glad you got it fixed too. i usually just clean mine because im too lazy to go buy a new one and install it, lol.
sux it cost you an arm and a leg, but look on the bright side: you can get a handicap parking permit now!