Robert Thomas

We were driving at 60 mph when the engine started missing, the tach needle was wildly swinging from 1500-6000 rpm and the SES light came on. The engine started running okay after a few seconds but the light stayed on. About 5 miles further the engine quit. After we coasted to a stop, I restarted the engine and continued to drive. It did the same thing twice more before we got home 20 miles later.

The only code it displayed was 36. The PO said the optispark was replaced 6 months ago. Hmmm...

I got out the FSM and checked the DTC 36 trouble shooting chart. It called for testing the voltage at 2 points in the optispark wiring. I found the 2 connections and tested the voltage. The book said the end result was either a faulty optispark or the connections or wiring were faulty.

I firmly reconnected the wiring (the opti connector was fairly easy to disconnect I thought after thinking this out) and cleared the code. I started the car and it ran fine. It was night by then and I live out in the sticks so I saved the test drive until the next day.

Yesterday my wife and I went on a 60 mile test drive in 107 degree weather on winding roads and on I35. The car ran great. I drove it 35 miles to work this morning and it's still running fine.

I guess the point is to follow the FSM and don't automatically assume the optispark is bad.

Bob Thomas
40th coupe

active1951

Is your car still runnin ok?
I have a similiar problem on my 94. Connections are fine, but all my tests point to optispark, PO replace it 6 months ago(AC Delco unit).

Robert Thomas

Well nuts. The engine died again today. It started right away and got me home 20 miles away. The FSM leads me to think it's still wiring. I'm checking it more thoroughly in the morning.

Bob Thomas
40th coupe

96GS#007

Many times people break the plastic clips on the electrical connectors. Make sure those are still intact on your Opti harness or the connector will simply work loose due to vibration. While you have the harness out, also take a magnifying glass and inspect all the pins for signs of excessive wear and/or corrosion.

active1951

Wonder which one of us is gonna get dirty and replace the optispark first, me or you?

Wonder which optispark we are gonna purchase?

Robert Thomas

I hoping not me but I'm planning on having to replace the optispark. I'm thinking of getting either the Chandler or KMJ.
Thank you for the advice, Jim.


Bob Thomas

active1951

A direct quote from PO of my vette:
"Sorry to hear that. If it is the Optispark, I would be a shocked.
The Opti in the car now is an AC/Delco unit.
I originally tried one from Chandler Motorsports. When my no-start condition remained and I exhausted all my diagnostic skills, I took it to a local garage.
Based on their experience, they insisted that after market engine electronic parts are incompatible with these cars. Regardless of what the aftermarket manufactures say.
So they swapped out the Chandler unit with the AC/Delco unit and the problem was fixed.
The part that was most perplexing was all those endorsements from users on the corvette forum. If it worked for them, why not for me? I don't know. All I know is that it didn't work for me and after the garage installed the AC/Delco unit the car ran."

The C4 in a fine machine with a real weak link. I am a 60 yo, that has tinkered with vehicles most of my life. I am extremely OLD SCHOOL and do things that would be laughed at in these forums. Usually I figure a "cure" for weak links by myself or with shared info with others.
I am new to this forum and investigating other forums.
I have over 300k miles on another vehicle with original engine/transmission and DISTRIBUTOR.
Oh well, need to tinker some more.........

active1951

did you get a new opti?