Hi :) I have a 1996 TE magna altera that a couple of weeks ago stopped idling well. Did a bit of research and put it down to the isc. Took the old one out ..put the new one in and now it idles up around 2000 in park-higher when hot. Have taken it back apart that many times just trying to work it out-all hoses are good, o-ring is fine etc.
So anyway with all this taking it apart etc I noticed when the MAF was unplugged it was idling ok (although again when it heated up it went high). So I went and got some MAF cleaner and tried that- no difference.
Does anyone have an idea on how I can easily test the MAF in easy speak lol I do not want to fork out money on the MAF if that is not it (hence why I was trying to do things myself).?
Thanks for any help...it will be greatly appreciated...

A new ISC tends to throw the idle way off. Usually way too low, or too high, and it can take quite a while for the ECU to get it right. Try letting it idle for a while.

Have you checked that the new ISC (I'm assuming it is second hand) is in fact ok?

Measure the resistance across the two coils.
Two rows of 3 pins, measure from the outer pins to the centre on each row, you should get 4 identical readings.
If one reading is open circuit, the ISC will not be able to retract (increase idle) or extend (reduce idle), depending on which coil is open circuit.

Thank you for your reply. The isc is brand new so it should be ok? I have driven the car around, reset the ecu etc, that is why I was thinking it might be something further along....is frustrating. I was under the impression that the ecu is reset after 10 mins of idling and taking the car for a drive for half hour or so- can it take longer to settle and reprogram?
So if the isc is okay (which it should be for the price paid) do you have any ideas on what else it could be?

Taking the car for a drive doesn't help, the idle part of the ECU circuitry is not active once you put your foot on the throttle.
10 minutes of idle should be enough, but my TL had a low idle after a battery disconnect and it took ages at idle to get it right, needed to keep it from stalling with the right foot for about 20 minutes for it to come right.

Another possibility is that you or someone else has played with the air screw on the throttle body to get the idle up with the old ISC and now it is outside the normal range for the ISC to control idle correctly. If that is the case, wind the screw in slowly while the engine is running, warmed up.

If it is working properly, cold idle should be 1300 - 1500 (depends on air temperature) and drop to 800 when warmed up, then be stable when you turn lights, A/C on.

Okay I disconnected the battery left it off (again) for a few hours...then attached and idled for 20 minutes-did not touch anything..it idled at 2200. So I am going to try the screw if you can tell me where it is? I have not touched any screws...just put in new isc but it is possible the last person did

Big screw on the front of the throttle body.

Big screw on the front of the throttle body.

...Sometimes covered with a black plastic plug (though they are often missing).

Okay..that is the one with the nut on it too? I can see a screw and there is also a nut? Sorry for dumb questions..just do not want to touch the wrong thing..

No don't touch that one. It's on top of the throttle body, closer to the plenum chamber side, in a recess that's pointing kinda forwards and up. I'll see if I can find a pic...

http://www.oz951.com/hostedpics/cts4.jpg

Ok, in the pic above ignore the red arrow. The air screw is in the D-shaped bit that's sticking up on an angle on the left, above the black throttle position sensor. It often has a black plug covering the screw, this just pops out. The air screw itself is plastic so don't force it if it doesn't move easily or you'll just strip the thread. It sounds like you might need to wind this in a bit to drop the idle revs but note that the ECU automatically adjusts the idle speed via the ISC so if the revs rise up again there's something else wrong. Also, only need to disconnect battery for 10 seconds or so to reset ECU, longer time doesn't make any difference.

Thanks for the help...the screw was pretty threaded but turned it one way it went higher ...turned it the other and its the same- as it was already tight and no room left to go. I don't know....the isc as been replaced, the maf has been cleaned, tried that screw, checked hoses, checked for air leaks, reset ecu etc etc -----so I am at a loss- I have been working on this for weeks-may be time to admit defeat lol.

I admit I don't know much about causes of fast idle, more common is slow idle problems caused by filthy throttle body insides. It sounds like the problem has been there for a while and has previously been "fixed" by someone screwing the air screw all the way in (which won't work). I can only suggest what's probably obvious, ie. make sure the throttle cable is correctly adjusted and that the engine gets up to temperature normally, all vac lines are fitted and not leaking, check that the throttle valve is actually fully closed with accelerator up, throttle body is clean inside, etc. Another possibility is that the screw you mentioned with the lock nut is not at the factory spec position. I think there's a section in the manual relating the correct initial setup procedure of the throttle body, I don't have access to the manual at the moment to check though (and mine's a later model, not sure what's different re the throttle body area). Otherwise I suggest it's time for the pros, if you know a good Mitsu mech in your area.