IAC motor I have a 94 chev lumia APV 3.8 liter. IAC motor goes to high RPM on start up and will not lower. Have changed IAC, Hooked Scanner to Van and tryed to control IAC manualy with no change. Checked wiring to computer, Power and grounds and to IAC motor. Also tryed new ECM. All sensor readings with in spec. Does anyone ave any ideas?

There are 2 most probable reasons for a high idle : Vacuum leak and IAC motor (Idle Air Control) is stuck in the wide open position. The vacuum leak could be a broken/cracked or hose that came loose or intake gasket could be leaking. Usually the IAC stuck open will have a code stored, but the best way to test it is with a good scan tool. A cheap (less than $500) scanner will not be able to test it, but any decent shop should have a scan tool capable of controlling the IAC to test it.

to get a cheap fix have a free fault code reading done
Then go to the wreckers /junk yards to get the failed part

check to make sure the power brake booster is not leaking, do this by starting the van and just let it idle in park and push the brake pedal if the engine stalls or surges or you hear a sucking noise under the dash then replace the power brake booster if there is none of these systems then replace the idle control motor. GOOD LUCK

Here is the firing order for the 1994 Chevrolet Lumina APV Van with a 3.1 Liter engine with a distributor, and the 3.8 liter engine had the coil packs, and let me know if you need any help to understand this diagram, or if you require any further assistance.

1-4-6-3-2-5

Seems you may have a varnished up transmission valve body, try the conservative approach first, have the trans serviced and flushed with transmission conditioner additive installed along with new fluid...

In 99% of the cases of GMs doing that it's the Idle Air Control motor, which you already changed. But changing it does not always fix the problem. First, if you bought the new IAC motor second hand, change it again cause last time i had to change mine 3 times before i got one that worked OK. Second, if it was bought new and/or your are 100% sure the IAC is working fine, then you probably just have to much carbon deposits where the motor's tip and the intake manifold meet and are supposed to seal up, preventing it from closing normally and giving the engine too much air, cause the high RPM idle. So take the IAC out again, clean the opening, lip and everything you can see and get into around that area, with a cue-tip and some contact cleaner, or lighter fluid or rubbing alcohol to get all the carbon deposits out and you should be ok. If not, then the problem probably resides in the car's onboard computer.

I bought my 2004 aveo 49 miles. I've had several issues with the car. But recently I been experiencung high idle at start up and clutching. I change IAC. Plugs and wireds. Nothing worked. Today the high idle became constant. It was a metal bubble flex tube near the IAC unit that goes to the exhaust stuff down behind the motor. It apparently was cracked cause today it broke causing the constant high idle sound like a vacumn. We blocked it off with a stick to get the idle back down to 900 rpm instead of 3-4000 rpm took we can get to auto zone for high temp hose per Chevy dealer. I hope this helps someone cause it was fustrating and costly.

I had the same problem with my van and ended up being the TBI base gasket

did you replace the iac motor or the tps , iac is the idle air control and the tps is the throttle position sensor