1988 Chevy Celebrity cooling fan runs, doesnt idle well in

First replace the engine coolant temp sensor for the ecm. Its located by the thermostat housing. I bet its reading too high causing your fan to run because it thinks the car is hot and also its making it run lean when its cold because it always thinks the engine is warm. The sensor has 2 wires going to it. I believe its a brown and a yellow wire. The part should cost less that 20 bucks. Hope this helps

Well unfortunately we need to install a scan tool at this time to actually see what the computer is seeing to find out if its a wiring problem or a computer problem. Is the check engine light on? Do you know the codes?

Tcc being unplugged wont cause any issues that im aware of. The code 63 is map sensor voltage high which can be set from losing spark or fuel. There are so many things that could cause this to happen. Im leaning towards the ecm (engine control module) I cant tell you how many I have replaced. If the ecm is reading the correct engine temp and commands fans on is a good clue that its bad and plus the code 63 is another clue ecm is bad.