just my 2 cents, it has to be fuel related as when not running it keeps re priming the fuel system, maybe a leak or something causing a pulse in fuel pressure so when idling it is affected.

or

What about the IAC my brother's Z24 cavilier did something similar to that and his IAC was shot.

 

Code 16 though?

 

You need to figure out why the fuel pump is doing that. Plain and simple. A fuel pressure guage and a volt meter will tell you everything you need to know.

 

OK I will check that first thing in the morning.

 

A 16 is the low res pulse from the opti to the PCM. Has nothing to do with the fuel pump and if your problem were low voltage on the system you would have had several codes OTHER than a 16 long before this.

A 16 will not set an SES but does disable the pump and injectors!

Stop wasting time looking at fuel for right now and focus on the low res pulse from the opti.

First pull the 4 wire harness at the opti and look at the quality of the pins in both the opti and the harness. Then check the connection about 3 feet back from the opti for the same thing.

If that looks good, the next thing I would do is go right to the black PCM connector and check the signal on the 2nd and 3rd pins (red/black and pink/black wires) with a scope. Has to be cranking or running to see the signal quality. I realize not everyone has a scope so you can use a multimeter across the 2 pins I mentioned. With key on, rotate the crankshaft by hand and watch the signal at the meter to change from near 0 DC to then 5 volts DC and then back again near 0 and repeated.

The reason for checking the signal at the PCM is simple. You don't know if you have an opti problem or wiring problem or even a PCM problem. By looking at the PCM, you either rule the wiring and opti in or out or rule in the PCM. Understand? Now if the signal isn't at the PCM or itermittently drops out, you go right to the opti. If it's at the opti and not at the PCM, you know you have a wiring issue. If it's not at either end of the wire, you know you have a opti issue. BUT I caution you. If you don't see the signal, check for 12 volts on the red wire going to the opti before you jump to conclusions.

 

PCM and harness is good, ive tried to different ones. I know I got to bite the bullet and buy another opti. I just dont think stop optis can handle 7k very long or the power od a digital 6 going to it.

 

If you're referring to the 3 foot section of harness that connects to the opti, fine. But there is still the section that goes from that harness to the PCM.

 

seems like it thinks the engine has rotated. thats why it keeps priming the fuel pump.
with my mustang i can turn the distributor a little bit and the pump will cut on momentarily just like yours.

i would look towards the opti. make SURE your grounds are good.

 

maybe ignition module.... get rid of the dig. 6 and see if it works any different first.

 

ICM checked good and it still does it on stock ignition.