In addition to what others are suggesting, you're in the problematic wiring harness years. Be wary of crumbling wire insulation in the engine compartment. Check the (blue?) wire to the ECT sensor on the block (s.b. under the intake manifold, right where you've been working). Idle is very much related to what temp the ECU thinks the engine is at. That's often one of the worst wires, also easy to accidentally have it broken or disconnected and not notice it. Also peel back the rubber boot on the IAC valve connector to make sure you don't have a short going on there, also the integrity of the wiring to the throttle microswitch. Might as well also test the microswitch with a meter just to make sure it's working. Like Phil suggested, has someone been fiddling with the throttle plate stop adjustment setting (screw with the lock nut)?
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Just one question: How does it behave when you put the old one back in?
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Art Benstein near Baltimore

Just found 2 lumps on my car battery.
Had them tested.
One came back positive.
Hope it's not terminal

Hi,

If it’s suffering from too high of idle no matter what, it likely to be the throttle plate is too far open.

The IAC valve should race the engine up automatically each time you start the car or when releasing the grounding wire. No need to pump the pedal and if the above is not set low enough, it will seem like it’s not working and then it’s the other problems that are being introduced to mess with everything.

Back off the idle stop screw so it can get fully closed And then, reset the throttle switch body to click just when the throttle plate begins to wiggle.
The throttle switch tells the ECU that you want the engine to idle and when to go into powering up mode.
The knob on the throttle body should be just about all the way in too.
It is only used to get the engine not too die when using the grounding wire in conjunction getting the IAC valve locked out of operation.

Now, if the engine just will not hold up it’s rpms and it pops and flutters into a stop, then it more likely getting too much air in someplace behind the AMM. The accordion hose can get cracked in several places with age.
HOSES are the number one suspect or a bad intake manifold gasket, especially if it’s never been changed.
It’s not a hard job to do and by doing it, you can get a good look at all the hoses everywhere.

Hope this helps you find the air mixture problem, that it sounds like it has?

Phil

Just 2 questions.
Is it the same part number?
Is it installed with the correct airflow direction?
Not being condescending.
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Post Back. That's whats makes this forum work.