1997 Chevy Express Engine shuts off when hot

Get a fuel pressure tester on hand

Duplicate the problem and immediately check the fuel pressure when it dies and comeback with the fuel pressure readings.

Do you hear the fuel pump every time you turn the key to run?

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.

When the last time you had it tuned-up?

Hesitating or stumbling can be caused by the following:

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires

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.