Aloha all, I've been searching and testing an issue with my 90 corvette. After warmup, It is backfiring into the intake and giving a code 93. I found a few test procedures that say check the voltage on the knock sensor and resistance. My resistance is good at 3.9k ohms but the incoming voltage is 12vdc (11.9), it should be 5 correct?
I have not been able to figure this out? Where is 12 volts coming from?
Should I purchase a new ecm to install in the cap, or could it be the electronic spark controller. Sitting down with my electrical supplement tonight, just thought I'd pick y'all brains to see if anyone has had something similar.

1990 corvette, edelbrock heads, hot cam, 1.6 roller rockers, double timing chain, superram intake, 21lb injectors. Currently saving for a bluetooth ALDL cable then some Moates programming gear. Thanks for any reply.

Found this on internet.

 

Ttt

 

I have an 89 which has no engine performance mods and is being restored to running and eventually racing condition. It has given me the same code which as I recall has something to do with the electronic spark control. I do not have any issues with backfiring though and it is not coming on all the time. I have not driven it much but only seen the code once.

I can't see how this has anything to do with the knock sensor. If there is question about that I would disconnect it and see if the code continues.

I don't know the condition of your ignition system, but in the past I had a Camaro that ran fine cold but when it warmed up it would backfire. In that case it was old plug wires allowing the spark to cross over to the wrong cylinders - they looked fine! It was also kicking a code that was due to the spark discharging into other wires under the hood. I would start with a dark test of the wires. Run the car in the dark and look for spark crossing wires. After that I would question the cap and rotor, followed by the remaining electronic ignition components.

I know that doesn't answer the question about the 12v power supply to the knock sensor. Have you chased that wire all the way back to it's source? Is it possible that 1) it was rewired incorrectly or 2) more likely two wires are rubbing together and the insulation is off and some 12v source is leaking into the wire.

 

Thanks, I'll check those things as well.
plugs, wires, cap and rotor are all new and the ESC still pulling the timing. If I disconnect the ECS barrel connection on the firewall, timing doesn't change.

I did find the following links helpful and hope they help someone else as well.

I'm not ready to put a resistor in just yet. I'm ordering a 1320 Electronics data cable next week and will back track the mysterious 12v next week.

http://pcfred.com/Vettetip/ECM%20troublecodes.htm

https://www.corvetteforum.com/forums...circuitry.html

 

95% chance the new parts eliminate the light show possibility. I have seen new cheap Autozone wires unable to contain the energy from the coils, and I have also seen new Accel plugs that leaked electricity through the ceramic insulation.

Did you have this problem before you changed those parts? In my Saturn I had iridium plugs and they do not like the old school coil packs it burns out the plugs. Basic copper plugs are better for the HEI.

Did you end up replacing the coil then?

How are the bushings in the distributor, as well as the pickup ring? These are also long shots

 

Aloha All,
I hope everyone is well during this craziness in the world. I have had some time to play with the Vette. I now have the car together, it runs even with the T56 conversion and just had the computer/chip reprogrammed. (Thanks Howellefi.com)

I set the timing and she is running okay. But have a code 42, 43 & she misfires/backfires into the intake going up any hill.

Any thoughts? This weekend I'll pull out the electrical supplement and trace it out. Just looking to see if yall have any thoughts or something I missed.
Thanks and be safe!

 

Aloha all,
I have the factory service manual and can not find a connector. Any assistance? Whetr is the Ignition Diagnostic Connector? According to the manual it looks like this. Thanks in advance and be safe.

 

It's a glorious day, I have the car back together for the first time in almost 2 years. She kinda drives okay it has a back or missing fire once she heats up and under power, but think its related to a code 42 & 43 that appears after it goes to open loop. (heated up)

Troubleshooting and thinking it may be the ignition control module. I also got a good deal on a new Accel distributor 59109 to replace the original. So will swap the new distributor and new module next week. Hope that clears up the 42/43 codes.

 

Aloha all, I found my code 42 which was the ignition control module, I got real lucky an scored a Accel distributor with and Accel control module off Ebay.
Then found a faulty knock sensor connector on the knock sensor side.

and oddly the datalog shows it running lean under load and misfires in the intake.im so close. If anyone has any suggestions please let me know, thanks to all!
it will be back on the streets as soon as Hawaii prints my registration.