Is there any part on a 1985 f150 that would cause a pip to short out? I replaced the distributor assembly and the ignition module about six weeks ago the truck ran excellent for about a week then started stumbling at cruising speed and became so bad until I replaced the distributor again, then it ran about a week or two and started stumbling, now this has happened again time number three. I am wondering is there anything in the harness that could cause this premature problem? I have also replaced the coil, wires and plugs,cap and rotor button

 

A short from the PIP circuit to power or ground might damage the sensor, but it would also kill the engine instantly, so I doubt that's your problem. I suspect you're buying cheap distributors. Buy an Echlin from NAPA or some other good brand from CarQuest or Parts+Plus. Even Advance & O'Reilly offer decent ones. Stay out of the zone.

But before swapping any more parts, buy a cheap digital multimeter & the oldest edition of the Haynes manual you can get, and follow the ignition diagnostic procedure in Ch. 5.