1998 Saturn SL1 Intermittant errratic running engine then s

I discovered the solution to my erratic running 1998 Saturn engine. Replacement of the Engine Temperature Coolant Sensor repaired the problem. The Coolant sensor directly regulates Saturn's fuel injection system. There was a small crack in the ceramic "pick-up" area of the sensor which created an open circuit over extended running times. I placed the sensor in hot water on a stove to re-create the engine operating temperature and measured the resistance with ohm meter. As temperature increases. Ohms decrease. After extended heat. The circuit opened (an open circuit should never happen) thereby stopping the flow of heat informtion to the the PCM, (car computer) which caused the fuel injection to go haywire and shutdown. Disconnecting the battery reset the electronics. But the faulty sensor repeated its failing performance at normal operating temperature, which is why the car wouldn't start immediatley, but cranked up the next morning when cold. You can use this same testing procedure to check the ohm resistance of the Crankshaft Position Sensor (heat can cause an open circuit on aging sensors). Lessons learned: replace all your engine sensors at 100,000 miles.