Car stalls and free revs after driving it for a half hour

I am driving my 84 seville with the 4100 motor in it and Im not sure of the transmission but its the one where the engine sits like a rear wheel drive engine but the transmission has cv axles so its front wheel drive. Anyways I was driving my car for short bursts of time and no problems. Now if I drive my car for more than a half hour when I come to a stop itll sputter real bad and act like it wants to stall and the rpms will rev high and it basically free revs. It threw no engines codes or lights and I checked vacuums lines and didnt find any problems. I was wondering if maybe the TCC solenoid is junk in it or the sensro on the torque converter is junk. Or if there is something else that might cause this. Let me know what you think.