GMC Repair: 1986 Firebird 2.8 liter high idle problem, point caution, coolant temp

Question
Have a 2.8 liter.  Idles at about 2k RPM after reaching normal operating temperature. Good idle while Engine is warming.  Replaced throttle body, ECM, new vacuum lines,remanufactured engine with about 20k miles on it. TPS replaced.  Any suggestions

Answer
Hi
I looked over schematics and everything I coul find.
Apparently, there is a cold start injector (Cold Start Valve) on the left rear of engine.
I am thinking this could be sticking on?
Also the only other few things I can think of would be Engine Coolant Temp sensor (reading excessivly low would keep the ecm "dumping" fuel in). Any Vacuum switch ANY that could leak manifold vacuum. EVAP purge, brake booster, anything vacuum can create this.
Lower intake gasket. Either leaking internally, or leaking externally. Some intake gaskets COULD be installed incorrectly and cause them to leak.
Spray carb cleaner around the intake, vacuum lines spray all around at high idle see if it knocks it down at any point. *****CAUTION around the distributor/plug wires  they can spark and cause personal injury******

Fuel pressure.... too HIGH COULD cause a high idle.

Base ignition timing and or the distributor could cause this problem. Timing too advanced will cause high idle.
Be sure to follow base timing procedure by disconnecting EST wire BEFORE timing.

Lastly and PROBABALLY not even worth mention, would be the Torque converter.  The converter is a fluid coupler. If the internal vanes have/had came loose the converter basically
"freewheels" and the engine follows right along. High idle is basic complaint.
This is RARE and would be the VERY LAST resort item I would consider. I would also take it to a Transmission shop to be properly and quickly diagnosed.

Again it IS possible the ECM could be faulty even a new one.
IF POSSIBLE, take it to a repair facility that can scan that older vehicle. Have them look at the Data. ECT should read correct. Should be in closed loop. A Good Diagnostician should be able to read all data and see if anything is out of normal specs.

I Really hope this helps.
Just advice from experience.
Good luck
Pawl