WHAT THE F%&#!!!

High underhood temperature could have actually caused a poor electrical connection to move ever so slightly & make better contact. Maybe your touching something while replacing your pulley & belt caused a bad connection to become better.

Good point! After some further errands this afternoon, it started acting up again(high idle), but not constantly.

Really getting puzzled now...I guess I needed more confusion in my life...

Maybe the added pressure and heat scared the shit out of it and it behaved for a bit? *g*

Not having a clue about the cumputer/fuel stuff, I'll take a WAG and say that maybe sensing the overheating condition temporally kicked the TBI to change the mixture??

Mac

Greetings,

I agree with the possibility that it may be a bad connection(s) that was somehow aided by either the high temps or the work you did. I would suggest checking the connections to the Intake Air Temp sensor and Coolant Temp Sensor (as well as the sensors themselves). A fault in either one could lead the ECM to believe that the motor is much colder than it actually was which could cause it to run at a higher idle.

Cheers - Jonathan

There is no Air Intake Temp Sensor.

CTS is new with new plug, as originally stated.

everything related to the TBI system. Thanx to

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Snip.

I assume that you changed all the tbi gaskets, including the alum. ring spacer between the top of the tbi, and the bottom of the air cleaner?

Forgive me if this has already been brought up.

HDS

Idle Air Control Valve ?

Mentioned and already cone.

Gaskets done.

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Hmmmm... dam.

Take the IAC out (Idle Air Control, on the back of the TBI with a 4 wire connection), and gently wiggle the plunger as far back as it'll go. Take the truck out on the road, get her warmed up and stay over 30mph for about 5 miles. That will reset the IAC.

I figure it's pulling air in somewhere.. vac hose most likely. But it's possible you got another bad IAC if you already replaced it.

Real stumper for sure.

Check list:

Fuel press. Fuel press reg inside the TBI (Spring, gaskets, and "membrane") TBI gaskets. Vac hoses PCV Air pump check valves (if equipped) IAC

Gremlins (Hard to find/kill)

HDS

Gone through 2 used IAC valves and one new. All doing the same thing. There is a wrong signal originating from somewhere that is telling the IAC valve to fully open. There is no black smoke at any time, so its not flooding in any way.

Like the follow up post I did(in this thread) said, after the overheating incident, now 75% of the time it is idling right at all temps(still not starting exactly right but acceptable, 1000-1200 at first start and 700RPM warmed up). Before the overheating, it was idling wrong

Shades, I agree that you could have an air leak. Check the throttle shaft in theTBI for slop. If the bushings or shaft are worn, you could get air leakage and/or the TPS could send out a false signal (I've only seen it twice but it does happen)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% "So why do I drive a big SUV? It's because I have to haul numerous people and things to places." ~ R. Lee Baxton ~

The throttle shaft is as tight as any I have felt.

I don't know if this applies to your situation, but I had a similar problem with a dodge 600 4 banger. It had similar problems. high idle, hard starting.

It had a bad head gasket, combustion gas leaking into the coolant, forcing coolant out of rad until the termostat opened.

After I repaced the head gasket, all the problems went away including the high idle!

Maybe the overheating caused the gasket to "seal up". Try checking the compression.

hope this helps!