Ok a weird issue.

I have a 76 Vette with a 91 L98 motor from a Camaro. I know there are a couple differences but I am hoping they are close enough, the Vette guys can help me instead of creatin an account on thirdgen.

I have searched, but this is a hard topic to search for. Basically, my obd1 CEL would ligh up now and then and go off now and then. Did the jump-2-top-right connectors thing to pull any codes.

The CEL did its thing and gave me an o2 sensor code, ok no prolem. THEN, I went to start the car. It fired and died almost immediately... key off, back on and the pump didnt prime... wait about 10 minutes, seemingly back to normal... weird. After several starts and wanting to ensure the obd1 was te issue... I ran codes again. o2 again. Not running again. Numerous starts, fuel pump not priming half the time... then 10-15 minutes later... good again.

Now, seems I have a stumble when I stomp on it in 1st or 2nd. Is this a common issue or some weird **** happening maybe because of something not done right in the engine conversion?

 

Did you fix the O2 sensor problem?

Also, check or add new Grounds from the Battery to the Chassis, Chassis to the Engine and Alternator to Chassis.






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No havent fixed the o2 yet, its a single wire o2 mounted after the headers into my side piping so I think I need to go to 3 wire so it can get to the proper temp.

But the weird thing with my fuel pump right after running codes... thats never happened to anyone? I didnt do anything or change anything... just jumped the 2 ports on the obd1 plug, turned the key to on and counted the flashes then turned it off.

 

You can energize the fuel pump by connecting a wire from port G (bottom row far left) on the diagnostic port, to the positive side of the battery.

Also, did you disconnect the timing wire before setting the timing? It's a single tan colored wire with a slim cylindrical connector near the drivers side firewall.





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1st.....

poor ground contacts will alter the data the ECM is seeing...so it alters the AFR and timing to compensate. Sometimes so much that it will not idle or it will create a stumble or misfire on acceleration. Solution?

Find, pull and clean ALL the harness grounds related to the ECM or engine controls. This is specifically about the ground bundle on the block near the oil filter.

Next, IF you have a jumper pole behind the battery with a few hot wires attached, CLEAN each of those very well. ANY of the small gauge wires off the battery positive terminal can corrode and give an irregular amperage/voltage to the ECM or engine controls. Again, the ECM uses resistance to read and manage data. If the resistance changes due to dirty connections so will the performance. AN intermittent CEL is screaming Bad Connection. Jumping the alcl a/b pins is the same as grounding the entire ECM mngt system. That's how the ECM controls when and what comes on and why....by continuous power to everything and the simple and safe completion of the grounds to stop/start various things. Electrical resistance is used as a means of gauging progress or signal strength. By grounding the alcl you are essentially turning everything ON. The fuel pump IIRC is the only thing independent of the rest of the system with its own circuit.
Pump should cycle on for 2 seconds with each rotation of the key to on/off. Until actual start up when the ECM will NOT run the pump again until it gets permission via a signal from the distributer that says its running without starter help. FSM elec drawings will show all this good stuff in color.

An o2 sensor , single wire down by leg pipes is as useless as ******* on a chicken.

Move the o2 bung to the collector for simplicity OR go to the heated type if you don't mind doing the wire work.
O2 sensors generate voltage (very low) as a signal. That is the by-product of extreme heat. The further away from the explosion in the cylinder the colder the exhaust gas gets....and the less of a signal the o2 sensor can produce.