thanks for the responses. I'll post back with how things turn out.

My question is should the little valve be closed the whole way when it is off the car?

No. It should look much like you described it. You can apply 12V to the terminals briefly to see it operates freely, or use a soft wooden stick to move the valve through its range against the spring. At rest there's a default opening. As it begins to move it will first close, then open fully.

Surging idle is usually the result of a vacuum leak or air getting past a dirty throttle plate.
--
Art Benstein near Baltimore

It's always darkest before dawn. So if you're going to steal your neighbor's newspaper, that's the time to do it.

In my experience, the valve can sit at any position when off the car. You can flick the valve along its axis and get the valve to open or close. Testing procedures are fairly straightforward for the valve. Always clean the valve in an inverted position (connector up, valve air openings down) to keep solvents out of the valve body. Some valves can be carefully pried open for rebuilding.

Make sure its wiring harness connector is intact before going any further. Inspect the pins in the connector (the wiring harness side, not the valve's connector) and make sure they are all seated in the plastic at the same depth. The middle circuit provides 12v when the car is operating, so checking this circuit for proper voltage when the car is running should be the first diagnostic step. Also check for cracks in the IAC hoses--any leakage of air in this circuit will affect idle.

Lastly, check that the throttle body is properly configured. Remove the TB and ensure that the plate is closed and the throttle position switch is also closed. I opened the throttle stop screw and reset it to just barely touching, locked it down, and then set the TPS to click on the first move of the plate. Reattach the TB and confirm the TPS click is still happening on the first turn of the throttle cam. This stuff is vitally important.

Other things that I have found which can affect idle include proper function of the coolant temperature sensor and proper AMM adjustment (of course I am working with LH 2.2 on a 1987 240, so your system may be different). In my experience, disabling the coolant temp sensor at idle would control a high idle but would also cause a very rich running condition (I could really smell the fuel in the exhaust).

In my last battle with my high idle, the IAC wasn't getting 12v because the new wiring harness I had just installed had a faulty IAC connector. Took me about a week to figure that out, and in the meantime I went through three IACs in a vain attempt to diagnose it (so now at least I have plenty of spares). IACs are not cheap!

kourt
87 245
austin, tx