I have a 94 Z28 automatic It starts when its cold it will run for between 15 minuites and an hour then it will just turn off not to start again until it cools down. I have changed the ignition switch under the colum,the ignition module twice,coil,coil wire and opti (and waterpump just to be safe). When it shuts down I have 41 lbs of fuel at the schrader valve on the rail. I bought this car cheap because it wouldnt start my only accomplishment it getting it to start but keeping it running is another story.

 

When it shuts off, does it still turn over? If it does turn over then is it losing spark or fuel?

 

It still turns over just fine Its not getting spark or fuel I pulled a spark plug wire and cranked no spark I checked the injectors for power and I get power to them but when it is not starting no injector pulse any help would be much appreciated

 

Ok then check the connection to the optispark. Sounds to me like you are either experiencing a failing opti or bad harness connection. Since you are losing both spark and fuel, the opti would be your number 1 source of the problem since it controls both.

 

sounds like a bad opti or maby a bad wiring harness to the opti.

 

Heres a thread about the same type of failure. http://web.camaross.com/forums/showthread.php?t=418051.

To cut to the end of that post, you want to look at 2 signals. The low res signal coming out of the opti on the red/black wire and the 12 volts going to the opti on the red wire. The 12 volts on the red wire is easy. Grab the meter and check from the red to the pink/black wire to see if the 12 volts is dropping out when you begin to have problems. If it is dropping out, the problem would be the PCM. But more than likely it's staying there when the engine goes south.

Check the red/black wire to the pink/black wire with the meter set for frequency. Not all meters will measure frequency. The frequency is not important, just the fact that it is stable until the engine starts to crap out and then the frequency drops fast. If this signal drops out and you already proved the 12 volts is still there, the optical sensor in the distributor is going south when it gets hot. You can also check it by using the meter set to DC on the same wires with key on engine off, rotate the engine around by hand after it craps out and see if it changes from 0 to 5 volts. If it stays low, it's bad.

Incidentally, that type of failure of the low resolution signal will set a DTC16. It will also cause the PCM to shut down the injectors and the fuel pump but it will NOT set the SES light. Good luck, I hope you don't have to change the opti but from where we sit, it doesn't look promising.

 

I am going to test it tonight I hope that is not the problem because I just put a new opti in 3 days ago the old one was bad I just hoped the new one wasnt bad thank you for the help I will post with my results later

 

sounds like an ignition moduel not an opti
opti shouldnt really care if its hot or cold