1991 Other Chevrolet Models IAC probloms

RPUTECH

MEMBER
1991 CHEVROLET
V8
2WD
AUTOMATIC
175,000 MILES

I just bought a chevy 1500 extented cab and have to put it in the shop be cause of the flywheel. Before I put it in the shop the truck ran fine beside the miss it had it did cut off when I was driving it. The mechanic said it was running rough and hook a computer up to it check it, he never said anything about afther that. Afther I got it out, he said he coulld never figure out why it was running rough but it was good to drive. Afther a couple of days it started idling funny and when I stop at a light it ran for a few seconds and die. Afther afther a couple of weeks it got worser. I finilly unscrewed the IAC clean it and plug it back in. The truck wouldnt start at first intill I took it off and adjust the metal peices inside the spring. It started for a second and die. So I tried again and hit the gas it ran and I got off it die. Is the IAC bad of it was idling to low what should I do?

1 Reply

HMAC300

MECHANIC
48,601 POSTS

You should never pull the iac out and move the springed needle. If you did clean it, just leave it alone and then drive the vehicle about 35-40 mph and the iac will reset itself. But your TPS may be sticking as well. If this is a TBI unit and I think it is then there is agood possiblilty that the gasket belwo the unit is blown. That is a normal problem with TBI units. It causes a massive vacuum leak and will effect the idle. Also the hose going to the map sensor goes bad and sucks together not allowing vacuum to the map sensor which causes running problems. Also the hose going to the pcv valve gets soft as well so check all these things. Choke cleaner while running the engine and spraying around the base of the TBI will tell you if it has a leak there or not. If the idle changes it does.