My son's 96z lt1 stalls and sometimes won't start. Will stall even if sitting idling. No codes. No spark no injector pulse when problem occurs.
PCM, ignition module, position sensor all ok. Problem began day after bringing car home from tire dealer. New tires and rims were put on.GM Dealer is stumped, has eliminated all major components as the source of the problem. Any ideas? This is his daily driver and needs it up and running asap.

 

Check the Mass Airflow Sensor??? Something at the intake? I was running mine straight off of the MAF at the track cuz my CAI didnt fit with my new hood and the MAF repositioned itself so it was not reading the incoming air and would not idle or stay running.

 

I have no warm fuzzies even if a dealer claims they've ruled out different components. From what you describe with no injector pulse and no spark it could very well be the optispark. Check this out:

http://shbox.com/1/4th_gen_tech2.html#opti_test

http://shbox.com/1/coil_testing.jpg

 

We had one Exactly like that years ago. Replaced the opti and Opti Harness...All was better

With out the Opti Signal no fuel pump or spark. We would get spark but no Fuel pump. was very odd.

 

Dealer continued to troubleshoot today, thinks its the optispark. Had one put on in April, but before the wires were changed. Could arcing at the wires lead to damage of the optispark? The cap, rotor, maodule and distributor were all replaced in April. Can someone reccomend a good replacement or do you stay with delco? The wires are MSD 8.5mm. How does the MSD optispark stack up? Car is a daily driver, he doesn't race it.

 

The 96 and up ignition is stronger than previous years. Stock would be fine. I would stick w/ a stock replacement opti if that's the problem.
I don't think arcing would cause damage to the opti.
Do you know if the opti has been exposed to moisture?

 

The MSD Pro Billet opti has some mixed reviews. Some people have good luck with them, while others have a tough time keeping rotor screws intact among other small problems leading to failure.

Just stick to a GM opti. Do not buy the Opti from the dealer you have the car at, im sure they will hit you with a $500 optispark bill when you can get it cheap around $230 from one of these standup guys
http://shbox.com/1/4th_gen_tech2.html#Dal_and_Jason

 

I had that problem years ago. Turned out to be a MAF, vaccum issue.

 

well how did they rule out the pcm? did they try a new pcm and it still did the same thing? thats the only way to rule that out.

I'll have to read up on the opti to see how it could possibly be interrupting the inj. pulse and the fuel pump? is it cause with the opti out, its not seeing any crank rpm?

the maf can cause intermitent stalls and stuff, but you could unplug it and see if its that or not. it'll run on backup maps if you unplug it.

 

I'd check the fuel filter, fuel pump and injectors. These will not cause a code. You may have clogged injectors or leaking injectors.

 

Only water exposure was normal driving, and we have been under drought conditions this year...VERY little rain. The dealer actually replaced the PCM, ignition module, position sensor with new parts to see if it would correct the problem. Fuel filter is new. Dealer said when the car won't start it's not recognizing the cranking rpms.

 

It pains me to think with the thousands upon thousands of dollars of equipment dealer shops have they just throw parts at it and hope for the best? Are you absolutely sure those components mentioned were replaced? That just doesn't seem right. And I'm sure they've charged you parts and labor for every little component they've installed? If that's the case they should all be hanged by the *****.
After reading that last sentence I still think it's the opti. The '96 has a crank position trigger, but I think it's only responsible for detecting missfires and if it were to go bad it would not affect engine operation.

 

Dealer has temporarily replaced suspected parts w/ new, even has driven
30 miles to pick up a PCM. He's only charging the $80 diagnostic fee. He's ticked he can't figure it out. When we talk about the opti as a possible source, are we talking cap and rotor, module, or distributor, or the whole nine yards?

 

what about the antitheft . it shuts down the fuel maybe the chip in the key is bad ? you can check by looking at it through the pcm with a scanner .

 

Just picked up the car from the dealer...no charge went to the shbox website and noticed vacuum lines to the optispark. Does anyone know what role vacuum plays in the operation of the optispark? I know its wishful thinking but we just put this optispark on a few months ago and really hope its not the internals of that unit. Its not bucing as if it were a fuel problem.... Since it will start after sitting a while could this be vacuum buiding and releasing as opposed to electronic parts heating and cooling? Oh yeah...Thanks for the help so far...will try unplugging the maf.