Idle Problem

Tater · Oct 13, 2004

I have an 89 5.0 and it has some kind of idle problem..it idles at around 2000 rpm then like 5-10 sec later it drops to around 1200 and stays there..also when i'm driving as soon as i hit the clutch it shoots up to 2000 and then slowly drops down to 1200. The motor is stock except for pullies. The pullies have been on for a few months. It just started havin the idle problem out of nowhere. Any help appreciated

Tater · Oct 13, 2004

86strokerlx · Oct 13, 2004

Try searching the forums before asking this kind of question. I'm quite positive it's been answered at least a hundred times. This is the kind of thing that really makes people on this site mad. Good luck in your search.

5spd GT · Oct 13, 2004

Tater said:
I have an 89 5.0 and it has some kind of idle problem..it idles at around 2000 rpm then like 5-10 sec later it drops to around 1200 and stays there..also when i'm driving as soon as i hit the clutch it shoots up to 2000 and then slowly drops down to 1200. The motor is stock except for pullies. The pullies have been on for a few months. It just started havin the idle problem out of nowhere. Any help appreciated

Try cleaning your IAB (cylinder looking thing mounted to the side of your throttle body) with some carb cleaner...take off the two bolts after disconnecting it and then let it air dry out...do the same with the throttle body...blow it all inside with the carb cleaner...carbon likes to build up in both of those...

See if that helps...and disconnect the battery when doing this...

Good Luck w/ your problem

Tater · Oct 13, 2004

I've already cleaned both of those up..How can you tell if the IAC sensor isnt workin properly

jmd2914 · Oct 13, 2004

im having the same problem off and on, i just thought it was a vacume leak, cuz ive replaced my IAC, TPS, and cleaned my TB

5spd GT · Oct 13, 2004

That was my next thought: small vacuum leak...you can find it by spraying carb cleaner around suspected areas...be careful...it is flammable...the idle will change...

I know with my vaccum leak I had it would rev to 3k right after I start the car and then kill itself...a bit more severe then what your experiencing...

Might aught to clean the wire in the MAF (in the "circle")...with a Q-tip with some carb cleaner on it...be very gentle because it wouldn't take much to bend it or break it...the "wire" is often clogged with air filter film...(aftermarket air filters)...

Tater · Oct 13, 2004

jmd..youve replaced all that and it still hangs? I had this problem awhile back but it fixed itself and now its back. I'll give the maf a cleanin and see how that works out...if i unplug the iac should the idle drop down or what? Right now if i unplug it, it has no effect on anything. If it was a vacume leak, wouldnt the idle stay high constanly and not drop from 2k to 1.2k after about 5 seconds, also could a sticking egr valve be the culprit?

jmd2914 · Oct 14, 2004

the sticking egr vavle could be it, but the vacume leak depending on where it is can close and open when the hose expands and contracts, i think thats what the problem is with mine cuz ive pretty much replaced everything else

Tater · Oct 14, 2004

Ok well i cleaned the iac , maf, and around the throttle body blade. None of that worked so i tried the base idle reset that i found in another thread and itdropped the idle back to normal after i did the reset...but then after driving it for like 10 min the idle went back to messed up like before. Does that mean my iac is broke and need replaced?

2002BLGT · Oct 15, 2004

Tater said:
Ok well i cleaned the iac , maf, and around the throttle body blade. None of that worked so i tried the base idle reset that i found in another thread and itdropped the idle back to normal after i did the reset...but then after driving it for like 10 min the idle went back to messed up like before. Does that mean my iac is broke and need replaced?

Im having the same exact issue , going to pull the upper intake in a day or so hopefully , everybody is leaning towards a vacuum leak being the cause ....

Tater · Oct 15, 2004

I went and put a new IAC on this morning and so far so good.

2002BLGT · Oct 15, 2004

Tater said:
I went and put a new IAC on this morning and so far so good.

better luck than me , new one on my car and its doing the same thing , new egr too ....maybe ive got a gremlin under the hood holding the throttle open LOL ......

HISSIN50 · Oct 16, 2004

when IAC's go south, they normally dont allow enough air to pass (not too much) - the result of the former is a low idle/stalling.

if the EGR was stayin open at idle, the car would stall (at idle), not surge.
i would pull codes.
good luck.

mustangdaren · Oct 16, 2004

Pull apart the two wiring harnesses behind the intake and clean them. Reapply dieelectric greese to them to prevent water from getting in them after you clean them. Another thing to check that will definitely cause this problem is your grounds. Check your battery connections to make sure they are clean and tight. Check the ground strap behind the intake from the motor to the firewall.

2002BLGT · Oct 16, 2004

mustangdaren said:
Pull apart the two wiring harnesses behind the intake and clean them. Reapply dieelectric greese to them to prevent water from getting in them after you clean them. Another thing to check that will definitely cause this problem is your grounds. Check your battery connections to make sure they are clean and tight. Check the ground strap behind the intake from the motor to the firewall.

yea I planned on doing that and probably installing an adjustable FPR (for future NOS ) while I have the upper plenum off of the car (for checking vacuum leak), shouldnt take long Ive worked on so many of these cars I can do it in my sleep .... going to get some carb cleaner and contact cleaner tonight , after this there is nothing left to do but swap ECMs .....

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