Check the simple things first, like all the vacuum hoses connected to the intake manifold. The rubber should not be hard and inflexible, esp. at the ends where the hoses connect to hot metal components. Get a piece of rubber hose and use it like a stethoscope to listen all around the intake for leaks. A brief spray of carb cleaner at a suspected leak point will cause a change in idle speed if there is actually a leak and the fluid gets sucked in.

Your K-jet system has a constant idle speed feature - a little electronic unit that tries to keep the hot idle speed at around 900RPM by adjusting the Idle Air Control motor. If the IAC is worn out and/or sticking it can generate the symptoms you describe. The IAC is only called into play when the throttle switch detects a completely closed throttle. If that switch is misadjusted it fools the IAC. On my son's 81 K-jet the IAC is not under the intake manifold (but it is on my daughter's 83 LH-jet), it is bolted to the cam cover in a rubber insulated bracket between cam cover and intake manifold. It's a black, cylindrical unit about 2-in dia X 4 in long with two 1-in rubber tubes coming out of its sides and disappearing down between the manifold runners. And it has an electrical connector from the wiring harness plugged in to one end. The big rubber tubes are tightly jammed in there and engine vibration can erode them clear through where they touch the manifold.

I would hesitate to use brake cleaner on it (or any engine component with electrical connections) but perhaps carb cleaner would be OK. Others will know.
--
Bob (81-244GL B21F, 83-244DL B23F, 94-940Sedan B230F)

I think you're right, leave #1 for last. That ignition system is terrible, so touch it as little as possible. Spray corrosion inhibitor everywhere. Read the bottle first- it should be non-conductive. But don't do that until you solve the idle problem. What do you mean by 'sleeves'?

2- Vacuum is generated by the motor, and it wants to keep it. If one of the hoses that routes the vacuum around the car leaks, the car sucks in air it doesn't need and then is running fuel-lean, or just stalls. This could be the problem, but it wouldn't be a small leak. Check to make sure all the rubber hoses are nice and tight, and don't have cracks. Sometimes they'll crack at the connector, move it around to check. You might be able the shorten the hose a bit and re-use it. Keep them clean of oil, and make sure nothing's vibrating against them that could cut them over time.

3- A dirty throttle body could be it also, easy enough to clean, you should at least remove the elbow and look up in there with a mirror. The biggest problem there could be a blocked vacuum connector, and that can only easily be checked by removing it, although you could attach a vacuum tool like a Mityvac and see if the ports are clear that way. Don't use carb cleaner, you're supposed to use 'throttle body cleaner'. Read the FAQ under 'Features'.

Another suspect could the idle air motor. It sits under the intake manifold, has one electrical connector and two 1 cm or so ID rubber hoses. Take both of the hoses off and spray a small amount of cleaner in here. Maybe brake cleaner, maybe someone will tell me I'm nuts, use whatever you like. There's a little vane in there that the electrical motor opens and shuts at different frequencies as needed. If this stops working, it could easily cause this sort of problem, as it controls idle. I'd check that first. Make sure the hoses are tight and clean when you're done, at both ends of each.

Good luck-
-Dylan