1997 Chevy Express Engine shuts off when hot

I can not duplicate the problem it only shuts off when outdoor temps reach 90 degrees or more. I will check the fuel pressure. It hesitates all the time.

Let me start again, this has been a long Time problem. It started Aug 2005 (180,000) miles engine would shut off while just driving along. Would not restart for and hour or so. It was diagnosed as needing a tune up and finely an ignition module. Tune up included new plugs - wires - distributor cap - Rotor button - Fuel pump and two electronic modules one located in the distributor and one that mounts somewhere on valve cover. All was GM parts. After this it did not shut off for a while but began hesitating when engine was not in a pull. About a year later when out door temps get 90 degrees or more it shuts off and will restart in a few minutes. Once it begins shutting off it will do it every 10 to 20 minutes. And it has never set a code. Hope this bit of history helps.
It has been a while since a tune up. But wouldn't these set a code. It has never had check engine light come on. The light is working comes on every time I switch on the ignition. I have never done anything to the injectors. Maybe I could have two different problems.
Thanks again.