After replacing the intake manifold gaskets, I have high idle. Timing is correct, no vacuum leaks, seems like the idle air motor is not controlling. Replaced TPS and Idle motor. Somehow I got the idle motor to close or nearly close by turning key on and off or disconnecting battery, don't remember the magic combination. Verified this visually. Disconnected connector from idle motor. Idled real smooth at 350 rpm with 17 inches of steady vacuum. Drove it this way for a week with no problems and steady but low idle. Plugged idle motor back in today, restarted, idle jumped up to ~ 1200 and after about 10 seconds jumps higher to around 2500 rpm. The problem seems to be the idle motor will not extend to cover the bypass port enough to bring idle to 600 like it used to be. Once or twice when starting on cold mornings it did seem to control until warmup then jumped up to the 1200/2500 range again. It is kind of warm here in the mornings now so the startup idle starts at 1200 the jumps higher after 10 seconds. Any advice would be appreciated.

Thanks.

 

Probably not the same problem but my 95 had a bad connection between the harness and the TPS. Even a new one didn't fix it. Problem went away when I replaced the TPS pigtail on the harness.
I could get the idle speed to jump up and down by wiggling / pulling on the connector and wire. Just a thought though. I checked every connection all the way back to the PCM but they all were good when the engine wasn't running. The high idle would come and go which was real fun when trying to stop quickly. Never. New if it was going to do it or not.

 

Thanks for the reply. Connections seem good. I am looking for info on idle air motor operation now. This morning i removed the motor, extended the "pintle" then re-installed on the throttle body. this puts the air bypass in full close. Restarted the vehicle, idle air motor did open up but too far letting in excessive air causing high idle. Not sure what command makes this device respond. Should the idle air motor go fully closed when turning the key on?
I didn't have this problem before the repair. I think 17 inches of vacuum at idle is ok. If there were a leak, the idle motor should go to full close to attempt to compensate for that but it doesn't.

 

As far as I know the IAC runs off a combination of throttle position, manifold pressure and a target idle speed. I think the target idle speed has little to do with it though.
This is what I picked up from toying with TBI injection so things might be a little different on the new. Basic operation has to apply though.

Have you run a scanner while it has the problem happening? A good scanner will show throttle position, manifold pressure and IAC counts for how far open it is being commanded.

I think you are correct that the motor should close down and then will open to a specified 'park' position.
The idle air motor will also open and follow the throttle position so the engine has air when letting off the throttle.
Hence why carbed engines seem snappy when the throttle is let off quickly and fuel injected drops off slowly.

 

A friend of mine did put a sanner on it but unfortunately his does not have the capability to display IAC pulse counts. All looked normal except he thought the timing was rather advanced.
It was ~ 21 degrees at idle and the low 40's when revving the engine. I checked the distributor position and all lines up perfectly. The car does not ping at all even under full acceleration.
I am starting to think this was pre-existing problem before the repair. Upon completion, I cleaned the throttle body and IAC ports with carburetor cleaner. There may have been enough gum
and carbon between the IAC pintle and seat to reduce the air flow. Removing it revealed the problem. Not sure though. I am looking for a scanner now that displays pulse counts.

Thanks for your ideas.

 

I pulled on each of the 4 IAC wires. One came out of the connector. There are 2 winding on the IAC, one to open, one to close. The bad connection must have been on the close circuit. This kept the motor from closing down the air bypass resulting in high idle. There are 2 crimps on the pin, one to secure the wire, the other to secure the insulation. From the factory, it was obvious the insulation crimp was never made. This resulted in the wire crimp being put under stress and eventually failing.