Need help diagnosing Dodge pick-up

We have a 1990 dodge pick-up, part of the family, great for hauling stuff and want to keep it but, when the temperature outside hits 90+ it will die and won’t run until outside temp decreases. We have taken it to 3 mechanics and nobody can find anything wrong. Suggestions?

Need more information. What engine, type of ignition (DIS or Coil & Distributor), and EFI or Carb? I’m leaning towards an ignition problem, like a bad ignition module or a bad fusible link somewhere. If it were fuel, there would be studdering problems whenever it ran in temps just below 90.