1987 ford van while driving we have skip like a cylinder is missing

van has 116000 miles, oil changed ever 3000 miles ,i’m the third owner, my mechanic has changed plugs, wires, distrubutor cap,antd the inners, check for vacuum leaks and have found none. It has a 302 fuel injected engine.

Probably a coil breaking down under load. But there are 100 other possible causes like a gummed up injector. Or low fuel pressure. Or plugged fuel filter.

What “inners” has he replaced so far?

when i said inners i ment points and condenser that is if it has these

fuel filter has been changed

It doesn’t.
My inclination at this point would be to put it on a scope, run the engine up, and see what’s happening with the ignition system. Has he done any diagnosis with analytical equipment?

Check the voltage at the coil positive terminal, low voltage could be causing the miss under load.