[efficientsteam]

My 1994 Z28 will crank and run for about 3-5 mins and then just die like you've turned off the key. You let it sit for about 12 hours and it'll crank right up. When it runs for the 3-5mins it runs perfectly. When it dies I have no spark or injector pulse.
I changed the computer out and the car is still doing the same thing. Its not throwing any codes. The VATS has been bypassed and I'm running a Delteq system. I've checked my connections at the opti harness and everything seems fine. I checked the continuity of the entire opti harness no problems there either. I really need some help. This is driving me crazy with my car sitting dead in my driveway. Please help. Thanks

 

[LiquidFire350]

i honestly have no idea, but just a few things im thinking, sounds like somthing is getting over heated and loosing a connection and once it cools its fine, kinda like how a blinker works, but i cant think of anything on the car that would opperate in that manner to cause the car to shut off

and does it have to be 12hrs? if after like 4 hrs it doesnt start?

 

[Chris 96 WS6]

I once had an optispark that would work fine for 30 minutes, then the car would cut off and not restart for 2-3 hours.....it was a bad optical section. Swapped the opti out and problem was gone.

 

[Vader]

He may be on to something (as long as we don't report him to the cops, he'll be fine).

Something may be heating and failing, and requiing a cooling period before it works (breifly) again. Typical suspects are an ignition coil and/or ignition amplifier module. Since the PCM will be looking for an ignition reference to administer fuel, that may account for both the lack of ignition and injector pulses. Of course, the same could be said of the optical array in the distributor.

 

[revolutionary]

Check all of your grounds including the computer grounds. If you have voltage going backwards at your computer then you definitely have a bad ground somewhere. If nothing else add another ground from your block to chassis. Also check for voltage and amperage drops to the computer and the sensors. May have a frayed wire that heats up and separates.

 

[efficientsteam]

Thanks for all the input. It doesn't have to be 12 hrs exactly sometimes its 8 or 10 but never less than about 5 hrs. I'm thinking if something is getting so hot that its taking 5 or more hours to cool off then I'd be having an electrical fire or at least smelling it. I've tested the ICM it tested good. The only conclusion I've come to is that maybe its the optical sensor. I hate to replace it and that not be the problem but I've been told the only way to test the low res signal from it is with an oscilloscope...which I don't have. Does anyone know if you have a bad opitcal sensor if it'll code? I don't have any codes. I'll keep everyone posted if I figure this one out. Thanks

 

[Chris 96 WS6]

The best way to troubleshoot this is if you know anybody with an LT1 you can borrow a coil and module from...swap those out and if its still doing it I can pretty much gaurantee its the optical section of the optispark.

 

[efficientsteam]

I reprogrammed the PCM and re-installed it. The car cranked right up ran for about 3mins and shut off. But, this time it coded!!! I've got to borrow the OBD scanner to get the codes. But hey at least I have a code now.

 

[efficientsteam]

Whats a fair price for labor to change out an opti?

Ok ok...it looks like its going to be the opti-spark. Can I also blame my wife's weight gain on the opti-spark??? It seems like with these cars every problem it has has to do with the opti. I was thinking about changing it out myself but after doing a little research I think it sounds like a ton of work that I'm not willing to get into. Whats a fair price to do this...labor only. And where would I find the best price on a good opti...not an auto zone reject? I had a quote from a mechanic of $350 labor only...is that a good price?

 

[Lifeisgood]

i would jump on that price, that sounds good, or he doesnt know what hes getting him self into.lol

 

[Chris 96 WS6]

I think for as small a job as that is $350 is a total ripoff. I can R&R an opti in as little as 3 hours. Lets just say I'm not busting tail...5 hours. At $65/hr typical labor rate around here that's $325.

OK, so $350 isn't that bad but still If I were close to you I'd do it for 1/2 that.

 

[camarojoe1991]

The VATS has been bypassed

This is kind of off topic, but whats VATS?

 

[efficientsteam]

Opti has been changed!!

I finally got off my fat rear and changed the opti out myself. And I didn't remove the air pump or alternator to do it. That bottom bolt on the water pump is a real pain without removing the air pump but with a lil coaxing and alot of cussing it'll come out. It cut my time in half. It was a piece of cake once I got that one bolt out. Yes it was the opti-spark. Its running like a fine tuned jet again. Thanks for all the encouragement.

 

[LiquidFire350]

This is kind of off topic, but whats VATS?

anti-theft, its that little resistor in you ign. key, stock you have to have that in there to start the car