1991 Dodge Colt Engine Stops Running/Cuts Out

This is a Colt Vista Wgn. Engine stops running. It's as if the ign. Key were suddenly shut off. Engine just stops completely, not stuttering, sputtering, etc. This happens when it's idling, running (even on freeway!), Anytime. Worked for a non-Dodge car dealer a while back and had that shop work on it. Their take was inconclusive. They suggested replaciing the module that attaches to a clip attached to the rear of the valve/cam cover. (It's about size of matchbook, but twice as thick.) That reduced the problem for awhile, but now it's back with a vengence! Car is running for shorter and shorter periods before engine shuts down. If shutting down at highway speeds will sometimes restart itself before coming to complete stop. If shuts down at low speed/idle will sometimes be able to restart it with quick flick of the ign. Key/sometimes will crank and crank and not restart without resting for short while.
Any suggestions? Any Dodge bulletins regarding this car? (I realize electrical ign. Problems are often the toughest to troubleshoot.)
Anyway thanks for any help.