Hello everyone, I'm new to the forum. I have a 97 Z28 with the T56. One night it decided to die on me and not restart. The Optispark was trashed, I replaced it and the engine still wouldn't start. I had a mechanic friend come over and we discovered that the timing was off by pulling the valve cover and rotating until #1 was at TDC. I pulled off the timing cover to inspect/replace the timing chain and discovered that the timing marks are still lined up. Could my PCM be faulty and advancing/retarding the timing? I'm kinda at a loss on where to go at this point.

 

what did you look at to make you think the timing was off? are you sure the opti was installed correctly. you can get them in wrong. can also get a new one that is not good. what opti and where did it come from? did you scan it for codes? did you test any of the systems/sensors?

 

Had a mechanic friend come over. No codes on multiple scans, both him and me. opti was installed correctly, on 97 will only fit in one way to fully seat. Got the new optispark from AIP Electronics. thinking that the reluctor ring slipped off the woodruff key and is confusing the PCM on crankshaft position. We did pull off a valve cover and rotated the engine to determine #1 TDC, seemed like timing was off. Going to double check it tomorrow or the next day.

 

crank sensor is used by the computer to test the system. it does not need it to run. so you got the ac delco 1104032?

 

All clocking/timing signals on the LT1 are provided by the Opti. In 1996 a crank position sensor was added just to detect misfires, and it has no effect on how the engine runs. If you believe there is a timing problem, take a good look at the Opti. If you installed a bargain unit, good luck to you.

 

Have you had the ICM checked? Have you checked fuel pressure? The opti can & has been installed incorrectly because I've seen it happen. Its a simple mistake that can happen.

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

Make sure you got the cam pin in the correct slot.