94 V6 3.4 liter Camaro--Car was running great, until went to pass another car. Then, everything shut down. Would not start, turned over hard--then when it would start, it would quit again. NO CODES are showing. When you put it on snap on scanner, it goes from closed loop to open loop and that is when it quits. It loses fire. It may start, but it stays in closed loop. It won't run long, then it stalls out again.

Already have: new plugs, new wires, new coil, new 3X crank sensor, oil pressure sending unit replaced (it was leaking), temperature sending unit was replaced (wouldn't read right).

Car will run fine for a week, then the problem will reappear. Now, after replacing all of the above, the car won't start at all? It stays in open loop instead. When it starts in open loop, it may only run a minute.

Anybody got any ideas as I'm running out?!?! Perplexed....... Could it possibly be the main computer?

 

had to add--the problem seemed to get worse after replacing the 3X Crankshaft sensor.....

 

If it dies when it goes into closed loop it is a good indicator of a sensor problem. If the car has a MAF, unplug the connector. This will prevent it from going into closed loop, but will set a MAF code, which can be ignored. With the scan tool interrogate all the sensors and see if their output makes sense, the one that is confused is probably the problem. The PCM can only pick up solid problems such as a wiring or connector problem, it has no way of knowing if a sensor's data is right or wrong, but you can.

 

Thank you for the suggestion! Going to take another look....