1987 Buick Century, 2.5 L, 4cyl, VIN-R:
I was advised by a very experienced mechanic that, based on my symptoms, the problem I had was solely caused by my transmission solenoid. Naturally, with this car being fwd, this would be quite an undertaking for the DIY.
As it turned out, my 2-core, water radiator started leaking real bad and required replacement. I replaced it with an identical, but 3-core, radiator.
Since then my tranny doesnt stall out on me anymore, no matter how hard I drive it! It may not have been necessarily due to the 3rd core, but the fact that my tranny is connects to and is cooled by that radiator, may have become clogged or poorly cooled by the leaking one, thus overheating the solenoid. This saved me a lot of time and money!
Just thought Id pass on the info.
It could also be that the transaxle heat exchanger ( in the radiator) was restricted causing the the lockup solenoid valve to remain applied at stops