Okay, now that I have the 89 ECM installed, nothing happened. The problem, as I now believe it, has to do with ambient engine bay and engine coolant temperatures. You see, when the engine is cold, it absolutely refuses to idle. However, if I let the engine warm up a little but (just over 100* or so), it will idle at 1000-1100 RPMs. Now, if I go for a drive, and the engine warms up to operating temperature or slightly above, the engine idles at 1500 RPMs. These idle speeds are not in gear without the brakes on, BTW. Also, possibly related, is the fact that my torque convertor clutch seems to have a similar problem. When the engine is below about 160*, the TCC locks just frigging fine. Anything above that, and I need more and more throttle to lock the TCC, meaning the speed at which the TCC locks increases the more I drive.

As far as the idle problem is concerned, I have replaced four injectors, all of the ignition components outside of the pickup coil, checked the fuel pressure (42 PSI KOEO and 37 running), adjusted the TPS (not quite sure what it's at now since I adjusted the idle speed screw, but the last time I set it, I set it at .60V), checked the vacuum reading (13-14" Hg), replaced the fuel filter, and replaced my factory 87 ECM with one from an 89 to delete the cold start injection (don't use it because the injector leaks and makes me run rich). The spark plugs are all normal tan/gray color.

The TCC has been checked for having a snug connector, proper TV adjustment, and does lock, so I know it works.

Can anyone help here? I'm thinking either the TPS, CTS, or IAT is bad...

 

No error codes?

Measure the resistances of the IAT/MAT and the CTS at a known temperature. Compare them here: