94 grand idle issue

[devanwon]

ok guys, im new here but have had a couple grands before...I just bought this and wanna fix it and drive it. so I have a 94 grand with the 5.2, 169k on the clock, the motor gave out about 165k but was replaced with another one from a wrecked 94 with 85k on it. so here is what I have its idling about 1100-1200 rpms, found that the trottle valve cable was broke so i ordered a new one but thats just for transmission sync with the trottle. what could be causing the high idle, it does have a flowmaster 50 on it but thats all everything else is stock.....where should I start checking or if someone know what to just replace. thanks!

also I climbed underneath and someone has taken the catalytic converter out and also put a flowmaster 40 series muffler on it... could this have anything to do with the idle? The O2 sensor is still in the exhuast.

 

[SteelHeadz]

Generally, high idles are caused by a vacuum leak either around the intake area or the t.body. Also check all the vacuum lines attached to the t. body all the way to the component it's attached to. Carefully look around the rubber lines attached to the fittings for cracks or improper fitment. IAC will also cause a high idle if the pintle gets stuck due to carbon build up. Cleaning the t. body and the IAC usually fixes that problem.

 

[devanwon]

Generally, high idles are caused by a vacuum leak either around the intake area or the t.body. Also check all the vacuum lines attached to the t. body all the way to the component it's attached to. Carefully look around the rubber lines attached to the fittings for cracks or improper fitment. IAC will also cause a high idle if the pintle gets stuck due to carbon build up. Cleaning the t. body and the IAC usually fixes that problem.

what is the IAC and where is it located? Took the tbody off and cleaned it, was not too bad in my opinion. used carb cleaner to see if i could pinpoint the vaccum leak, no ramp up in idle unfortunatly....The only loose vaccum line i found was on the drivers side of the intake in the midddle the small lines it was the rubber boot (the lower of the two small fittings) gonna get some small vaccum line and get rid of that boot as it is stretched out. other than that nothing. ideas?

 

[devanwon]

anyone?

 

[SteelHeadz]

The IAC is attached to the t.body. It's a cylindrical solenoid motor that has a plunger which adjust or fine tunes the air mixture entering the t.body. On the illustration, the IAC is to the right side of the TPS.

 

[Bounty__Hunter]

Did you remove all the sensors before cleaning the throttle body? Solvent on a sensor will cause a high idle for a short time even if you have fixed the problem, it usually corrects itself after some driving.