2003 Jeep Liberty car stalling; won't start til cool

Was driving along and heard a thump from the engine compartment and about 20 seconds later the car stalled, and the tachometer went crazy. I tried to re-start, but car wouln't turn over, although it did strongly crank. About twelver hour later, I tried to start again, and with a little difficulty, it finally turned over and ran smoothly for about 15 minutes when it stalled again. All gauges were normal, including the tachomenter. My mechaninc put a dianostic scope on it and it came bac {crank positiioning sensor", he changed, and idled the car for twenty minutes until it stalled, and woulduin't start again. Tried with another "cps" and it did the same thing. Took computer to a professional tester and bebuilder/exchanger cdompany. They said computer was bad. They exchanged one with me that they reprogrammed for my car. After installing, it did the same thing as before. Tried a second exchange computer with the same result. I need help. Is this really an electrical problem.(E.G. Computer, cps, etc.) Or is it something else?