I would go over the complete ignition system and ensure it's in great shape. To ensure the reliability and performance on older cars, this is imperative. Therefore, I would replace the Ignition Control Module (ICM), coil, distributor cap (pay particular attention to any O-ring seal), rotor, spark plugs, and spark plug wires. It wouldn't surprise me if the ICM and/or coil are breaking down under load (heat). Because of the age of the car, I would replace the ICM and not rely on bench testing.
Reading the link below may help:
https://www.askmehelpdesk.com/cars-t...tml#post520809
If the problem persists, see if there is a thermal overload switch that may be shutting the engine down to protect it from overheating. When I rented an Opel Capri, in Frankfurt, Germany, I ran into this problem while using the air conditioner in the heavy traffic in Genoa, Italy. The engine died in rush hour traffic and would not restart. As I backed up traffic, the Italians wanted to kill me. That night I suspected the car must be equipped with a thermal overload switch. In the morning, I figured it would start and be okay, which it was. I was just careful not to use the A/C in city traffic. I never had any more problems during the trip.