Well my car (91 accord) would shift through all gears fine in warm weather. When cold weather would hit, the TCC wouldn't lock up and gas milage would go down. :screwy: Also the temp gauge would run totally cold when crusin' down the highway and start to warm up when stopped at a light. I replace the thermostat and it actually fixed the problem. Does the temperature of the engine directly decide if the TCC locks up or is this just a coincident?

Yes, the TCC lockup, EGR operation, and a few other things are disabled until full operating temp is reached...