1989 plymouth voyager stalls after warm up

Question edited for clarity full year make model, 'set/sit' misuse.
Question moved to sub category.

For a fault like that, it can only be diagnosed by an auto electrician with a pro grade scan tool to record live data when it quits. You are the only person to have this issue on that make and model.

Sounds like a misfire. But honestly it could be anything. If the check engine light is on that could point you in the right direction

Have you checked base fuel pressure with a gauge ? Have you tested the asd relay ?

Sounds like a vapor lock in the fuel line. If the fuel line is a hose, then in summer time, the line , if it is old, will collapse due to vapor lock. This will cause the problem you are describing.

CRANKSHAFT SENSOR.

you may not have the fuel lines sealed, they can **** in air without leaking fuel, especially in the tank, whre the pump connects

This sounds like a fuel problem, I would check the IAS( Idle Air Speed) motor located on the throttle body , possibly a wire problem try wiggling them first to see if it changes the idle speed or stops the surging your referring too ! has a check engine light come on at ant time ?

did you try the crank position sensor?

What you have the cap and rotor.could be bad use good one.

try air flow meter