How to test IAC solenoid 1996 4.0

[98Chero]

I think I have found my idle problem ? The IAC ( Idle Air Control ) is not moving, but when I turn the ignition switch to on two of the four pins that connect to the IAC light up.I have already done a complete tune-up and checked for vacum leaks and all electrical connections are good. the problem started all at once on a cold morning, before that the engine ran good Im puzzeled ?. If I could better understand how the IAC works it might help me figure out the problem.

specs
1996 cherokee sport 4x4 4.0 engine automatic trans

 

[Bounty__Hunter]

Have you had the throttle body off for a good bench cleaning? The IAC will work better when clean as well.

 

[98Chero]

no I havnt took the throttle body off yet, I have sprayed some carb cleaner in the area of where the IAC goes and blew it out with an air compressor nozzle. I was able to make it Idle by putting a Dime between the throttle plate stop and the (factory set) adjustment screw on the body. I replaced the dime with a 1/4 rubber tube so I could run the engine at 2000 rpm so I could do a fuel pressure check with the gauge and it had 35 psi while running and held 35 psi after stopping the engine. this engine did not come out of the factory with a pressure regulator on the fuel rail so I could do that test. Does the IAC only move when the engine is cold ?

 

[98Chero]

So I put a new IAC ( Idle Air Control ) on the throttle body and it fixed the problem. I would advise that if you ever take the IAC off.. Do Not unscrew the plunger, apparently it is factory set. just clean it and the area it goes into period. the best i can tell the IAC stays pulled back during cold starts and as the engine warms up the computer tells it to close. My old IAC was stuck in the closed position causing the carb to have a lack of air during warm-ups. $40 here and another $40 their etc.. and my GF jeep is back on the road again so she dosnt have to borrow my ride anymore