Well with it acting out again, but with no codes this time, it could be number of things, maybe bad plug wires, coilpack, or fuel injectors.

This Ranger has a "waste spark" ignition system & as such, there are only 3 coils in the coil pack, to fire all 6 plugs.
So the plugs are paired such that one plug is fired on it's compression stroke, while it's companion is fired on it's exhaust stroke (waste spark).

So if we knew which plugs were fouling out, it might offer up a clue to your suspicions about the coil pack, especially if the acting out plugs were paired at the coil pack.

It's Not normal for the Ranger to have fouled plugs!!!!

If the plugs are carbon fouled, suspect a fuel trim problem. Maybe a clogged air filter, or a fuel pressure problem, or fuel injector problem.

Fuel fouled, suspect excessive fuel pressure, maf sensor, TPS sensor, O2 sensors, dirty or leaking fuel injectors.

Oil fouled, suspect sticking, worn, broken rings, worn valve guides, leaking valve stem seals, plugged PCV valve, wrong viscosity oil.

So maybe have him call his Tech & ask him for a "plug read"