Im still looking at that '88 TurboII
the owner reports that it has a slightly high idle, around 1100 to 1700 RPM even after the accelerated warm up sequence ends

 

And...............................do you have a question? If it is about the high idle, there is a awesome thread in the 2 gen archive. that will give you the best info IMO.

 

On a cold start, the engine is supposed to rev to approx 3000 rpm for 17 seconds, then the idle should drop to about 1300 give or take a few and gradually drop down to approx 750rpm.

The 17 seconds is due to the ECU and BACand airbypass valve working together for that period of time, then dropping out.

The idle at 1300 give or take is due to the thermowax and fast idle cam.

The 17 second job should only happen in neutral. Since yours does it in gear, then your neutral switch is kaput or disconnected.

IF the rpms NEVER drop below the 1100 figure you quoted then it could be the water thermowax and fast idle cam are disfunctional OR it could be someone has the throttle cracked open using the throttle stop screw. Or???? other things.

The first thing I'd check is for the fast idle cam coming off its roller or not. See the FSM, Fuel section for how to rig it right.