Not for your car.

I unplugged the #3 cylinder fuel injector and the #4 cylinder started to work. It was running on 3 cylinders, plugged the #3 injector back in and it was back to running on 2 cylinders. I have to find out what tells the injector when to spray, since it is telling the #3 injector to constantly spray a lot of fuel.

Spark is not a problem, too much fuel is the problem.

Is there a test to see if the O2 sensors are good? Wouldn't if the O2 sensors were giving false readings that affect all 4 cylinders and not just 1?

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Originally Posted by Peter 2001 SS

I unplugged the #3 cylinder fuel injector and the #4 cylinder started to work. It was running on 3 cylinders, plugged the #3 injector back in and it was back to running on 2 cylinders. I have to find out what tells the injector when to spray, since it is telling the #3 injector to constantly spray a lot of fuel.

Spark is not a problem, too much fuel is the problem.

Is there a test to see if the O2 sensors are good? Wouldn't if the O2 sensors were giving false readings that affect all 4 cylinders and not just 1?

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Key on, engine off: is the check engine light flash several times and then remain on steady?

Unless there is a problem with the engine and/or PCM harness, is still sounds like you have a faulty PCM. All the injectors have a common power feed. However, they are controlled individually inside the PCM. Close visual inspection of the PCM connectors is next.

The O2 sensors will "wake up" and feed data to the PCM once the engine is running and the O2 sensors and coolant has reached "Closed Loop"... until that criteria is reached, the PCM operates from predetermined open loop parameters and the O2 sensors have nothing to do.

Concentrate on finding the harness/PCM fault.

Did you every check for any codes being thrown? Problems like you're experiencing would have to throw one or more codes. The ECM controls the injectors and, based on your description, it sounds like your computer may be bad. Try and substitute a known-good ECM.

Last weekend I bought an Autotap. I have been so busy lately that I haven't gotten a chance to scan the car yet.

I scanned the Cavalier and have several Trouble Codes and 2 of them I had multiple times.
P0108 MAP Sensor Circuit Hi (3 Times)
P0200 Injector Circuit (2 Times)
P0713 TFT Sensor Circuit High Input

This problem was fixed a couple months ago now. The car is running great now. This problem was caused by a bad computer that was shorting out the number 3 injector.

I'm sure that was a difficult problem to isolate. Good job!