I have a 1991 notchback with an AOD. It seems that while at an idle in Drive the car temp wants to go up. I can pull it into (N) and the temp gauge will slowly go down. I've replaced the clutch fan, fan, waterpump, and had the radiator cooked and cleaned. Any info would be appreciated.

 

This sounds like a waterpump flow problem,or just as likely,a timing problem.Check the timing to be sure that it hasn't been allowed to change from specs.Make sure the cooling system is full of coolant.You might try some Redline Water Wetter.It acts like your problem is very repeatable so it shouldn't be hard to track down.

 

Get your block flushed.A friend of mine had that problem with his 88 camaro.You might also want to look at a bigger radiator.