weird ignition problem
 

My son's 1992 Protege is really baffling me. I have never seen a problem like this. The car normally starts and runs fine for a day or part of the day. Then, all of a sudden, it will sputter and die and while the ignition switch is still on, the ignition coil will arc around the high tension lead tower, and the tach will jump around, but the crankshaft is not turning. Without the engine turning, I really don't understand how it can generate a spark. I thought maybe the PCM module was acting up so we replaced it from the salvage yard and also the coil, but it continues to do the same thing. My next idea is to try swapping the distributor pick up module. Any other idea? Thanks.

It *can* still spark, because with the ignition still on the coil is energized.
I'm not quite familiar with the first gens, but are there any wires leading to/from the coil that might be exposed, or have bad insulation??