pjtikkanen

Hi:

My son has a 1994 Z28, and it had been running fine for about 6 months after he had the engine rebuilt. He put an aftermarket optispark on it despite my suggesting he get a GM original replacement because I had heard that most aftermarket optisparks are no good.

Anyway, the car will start, run, and at any time will just quit like you turned the key off. No check engine light comes on. We replaced the coil and ignition module, and took out the alternator and it tested out fine in two shops. If you leave the car a few hours it will start right up, runs fine and quits sometimes an hour later, sometimes minutes later.

Can a bad optispark cause this problem? It seems so odd for this to happen. I would figure it would either work or not.

Thanks for any guidance you can provide.

Paul

Kevin Blown 95 TA

Maybe your ignition switch or anti-theft module is acting up.

Also make sure the opti connector is in good shape with no corrosion.

1994v6cam

it could be the security system on the computer might need to be checked along with the wires

bobdec

VATs will prevent cranking and fuel injector pick during startup however for safety reasons it will not stop a running engine. Logic is if it started the VATs system (and key) was OK initially and therefore failure is circuitry. I know it's almost impossible to find someone with tools to get a '94 ODB1 scanned. The OPTI should throw a code if it dies (high or low resolution failures) the ICM or coil can, and do, fail quite often when hot w/o a code, but you already replaced them. Do the fans cut on when the car is restarted, a signal that a code was thrown.. You could be loosing ignition voltage, when the engine dies you should get a check engine gauges due to alternator and oil pressure going away. If no dash error lites it may be the ign voltage.

Savannah Dan

Give this thread a read:

https://www.camaroz28.com/forums/sho...d.php?t=652072

pjtikkanen

Thanks for all your suggestions.

When the engine stops the lights come on including the check engine light and when it starts and runs they go off as expected. We don't get any security light warnings. I had one of those on my 2002 Monte Carlo. That never killed the engine, but good luck starting it again! They had to replace some module in the dashboard and the trouble was gone. Gimme a 60's car anyday!

I will send this link to my son and he can start looking for any culprits like bad dirty connections, wiring etc and if he can't find anything then they will have to tear the front of the engine down and replace the opti.

Paul

Injuneer

Scan it for codes. The Opti optical sensor codes do not turn on the SES light. The two components of the ignition that are most susceptible to heat soak are the IC Module and the optical sensor in the Opti. Both should store codes if they are faulty, even if its an intermittent problem.

You indicated "no check engine light comes on", but later you said the "When the engine stops the lights come on including the check engine light". The only time the SES light should come on is for a few seconds at startup, then turn itself off. If its coming on when the engine stops, its telling you there is a problem, and its storing the code that turned it on.