Dying with heat makes me think failing electrical - replace your ICM yet?

 

A couple other questions/suggestions:

1) Have you used a timing light to verify that the timing is correct? If so, did you make sure to unplug the ignition control circuit when checking it? If not, warm the engine to temp and verify the base timing is correct - it should be set at 0* - it helps to clean the timing marks on the balancer and color it in with white out or equivalent.

2) If yes, unplug the ignition control circuit and see how it drives. If the misfire/jerk goes away, something related to the computer controlled timing is the problem - it could be a bad sensor input or the ECU - further diag will be required.

3) If it doesn’t go away, see if the speedometer or tach movement is erratic/bouncing at the same time the misfire/jerk occurs. If yes, you’re likely looking at a crank or speed sensor depending on which gauge is displaying a change.