Thanks to "Off-Roader" who directed me to this forum.

The dealer is telling me the Throtlle Body is defective.

The monty does have a new ECU, new Idle servo motor, new throttle positon switch. Replaced less than 3k miles ago at the same time because of the same symptons I have now.

Current symptom is high idle at start with the air screw adjust turned all the way off, and after a short warm up modulated idle varying rapidly between 900rpm to 1300rpm.

The dealer proved my throttle body was defective using the throttle body from a running vehicle they had access to. And they claimed to have used my new electronic parts on their spare TB pulled from a running monty. I saw them pull the spare monty into the bay next to mine. If they are pulling a fast one they have gone to a lot of trouble.

My question is couldn't the dealer just clean the throttle body. Like you would with a carb cleaning tank. When you take the electronic parts off the TB all you have left is a machined chuck of metal to pass air and control air flow.
My feeling is that my TB has been clogged up some how.

My other question is if the TB is more than just a passive part. What is active about it. There are vacum hoses. And the TB has coolant passing thru it. I have seen some devices on japanese vehicles that use engine coolant to heat up a device with wax in it to control idle.

Thanks for any input

You have a thermostatic first fast idle valve in the TB, plus the ICM, plus the manual adjust air bypass screw. The Fidle valve closes quite fast, before the temp gauge comes off the peg on mine. Possible to epoxy it shut, but tricky, as it shares the air port to the TB bore with the ICM. I've seen a very few go bad. I'd try a junkyard TB before I paid for a new one....

I was having the same type issues. I pulled the fast idle screw ( which was seated all the way) & replaced the o ring on it, seated it hard & retracted a few times, ran i a bit & found it lowered the idle.
FSM says to replace TB if idle will not lower.
I'd plug all vacuum hoses, including PCV & see what happens, then carb cleaner arount intake hose ( possible cracks) to diagnose it better.

Ed

more good info here..thanks

my question is this,
how much cleaning/service can be done on the TB without removing the whole assembly?

Clarification needed:
FSM says to remove the TB to check the IAC. Other sources seem to suggest that the IAC will just slide out without TB removal.

Throttle body is very easy to take off. 4 bolts and some hoses. Might need a new gasket, I reuse my metal one.

After doing it enough times, I pick up the right tools to pull either... LOL

It's a 3 minute job to pull it. Good time to replace the gasket, too. Could be an issue for ya.

FSM states to remove the IAC for cleaning, as solvents can wipe out the insulation in the motor.

As for the issue of backwards idle, If you're using the same plug, swap the wires around to reverse it. PM me for more info. we can figger it out wihth the FSM.

Ed

Many times a hunting Idle speed is not caused by the ISC. The ECU can be changing the mixture and timing rapidly cousing the surging.
To check for this, unplug the conector to the ISC while it is surging, you may find it still hunts.
I have two of mine doing this now, a V6 Mighty Max and an Evo III. The truck is more irritating since it drives closer to idle more than the car so it feels like I am jabbing the throttle when driving slow.
It might have somthing to do with the O ring since both of these has had the screw removed and replaced, I thought I put fresh rings on but may not have.

I would say there is nothing wrong with your throttle body itself.

Yes. Correct.
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If I need to remove IAC to test ...Does this require taking the Throttle-body off first ? (1989 model)


Thanks, it is good to hear from persons who have seen it before.

The IAC can be removed easily. Use 8MM socket & remove 3 bolts holding it on. then, just wiggle it out.

I would still suggest removing the whole shebang, though...

Ed

Check the pintle on the end of the ICM that seals the hole to the TB, and the seat it sits on for non sealing. Look very closely for cracks in the rubber hose from the MAF sensor/air cleaner to the TB, and in the short hose from the Pside valve cover to that hose.