IAC clean, TPS adjusted, idle...all over the place

My 90 5-speed had been running and idling well when that 2000 rpm miss started happening (again). I recognized it as the TPS being out of adjustment, so I adjusted it and everything seemed ok.
A couple of days later it started the high idle thing (which has happened before as well). So I checked the TPS again and the number had dropped from the .825 to .7something, so I adjusted it again, but the idle never got better.
Within the last 3 years, I have replaced both the TPS and IAC, but am suspecting a bad IAC again.
The idle is normal to low at start-up and was going up to 1300 after warm up. I took the IAC out yesterday to inspect/clean, but it wasn't dirty. After re-installation, the idle is very low on initial start up and now may go as high as 2000rpm, but verys with every traffic stop. When I had it out (but electrically connected) I turned the key on and it did not move.
Do I have a bad IAC again? How do I know for sure?
Thanks,
Scott

I should also say that the fast idle started with a vacuum leak I accidentally created when adjusting the TPS. I fixed the vacuum leak (I swear, I've used a large can of spray checking everyplace I can find!). Is it possible I lost the IAC as it tried to adjust for the vacuum leak?
I know this topic is asked to death, I did a search, but I could not find a specific test to determine whether the IAC is operating at all.

Adjusted the TPS? hmmm... must be different than my 93.... no adj. My first thought is to look for the easy and cheap stuff that fits your failure first. The very fist thing I would check is for a vacuum leak. I spray my lines down with Chemtool, a cleaner you can get ath the parts store, and check them and the EGR valve, the intake manifold, etc. with that. If the leak is small, it revs up. If it is big, it dies.
Start with the cheap easy stuff first. (And, in this case, one of the most likely things!)
Good luck with your reapirs...
TheRasper.

We must've been posting at the same time.... On the IAC, I would continue my search elsewhere first. The reason I say that is due to your indication that the idle changes from cold to warm, and is different at different idle times. This indicates that the IAC motor is working. You have to find out why it is working incorrectly. The IAC is controlled by the PCM in accordance with the information it receives from the other sensors. MAP, MAT, O2, namely. The compiled infor lets the PCM decide on an appropraite idle rate, based on information about running cinditions in the past 40 keystarts, or so.
Having said all this, I'd jump straight to the vacuum (yes, again!!!), especially at the MAP, MAT, intake manifold gaskets, and EGR valve. Next, O2 sensor. It should have a resistance reading of 5-7 ohms. If it seems at all marginal, replace it. I am guessing by now the problem will be solved.
If you need to ck the MAP/MAT sensors, consult the FSM, it is a little too "wordy" to get put in here...
Let us know what you found, please.
Best of luck with your repairs.

TheRasper.

Here are a couple more less mainstream things to look for. First, make sure the MAP sensor line is correctly connected at the throttle body and the double plug isn't upside-down. Also make sure that the throttle bell crank on the side of the engine is not worn and binding, and that the accelerator pedal pivot is not binding. You can't troubleshoot the electronics if the throttle plate isn't closing the same every time. And make sure the vacuum line for the crankcase vent isn't cracked or loose, including a hardened grommet at the valve cover, which can cause hard-to-trace vacuum leaks.

Thanks guys, I've gone from my best mileage (over 22 on a highway trip) to my worst mileage 16-17 in a matter of weeks!
My EGR is and has been blocked off for years (the controller on the inner fende is bad, the EGR works fine if you suck on the tube, the vacuum source is blocked off). I've had the throttle that doesn't close all of the way before, fixed it and checked it, that's not it.
I swear in 3 years I've had pretty much every common symptom posted here! I've replaced most sensors, not the MAP, but it tests out ok.
What I did was I cracked the vacuum tube going to that nasty little vacuum tree in front of the throttle body when adjusting the TPS. When the idle went up, I started looking for a vacuum leak, found it and fixed it with epoxy. I checked it with throttle body cleaner, but it just hasn't run the same since.
I doubt I have a new vacuum leak anyplace else that just happened to spring a leak at precisely the same time I adjusted the TPS! But I've sprayed everything, even the 4WD lines!
I'm going to cap off the vacuum to everything but the fuel rail and see what that does. I still think that something is up with the AIC because taking it out looking at it and putting it back in has changed the way it runs. Also, I do not entirely agree that the change in rpms indicates that the IAC is moving because if it is stuck in one position, the "vacuum leak" that it creates would most likely lower rpms when the engine is cold wouldn't it? And since it doesn't move as required to maintain a proper idle, idle will vary with conditions, right?
So that puts me back to my original question, how do I test the IAC? Should it move when the key is turned on?

Sorry, something else I just thought of. I took the intake hose off and putting my finger completely over the IAC intake lowered the idle well below the normal idle rpm.