OK, resistor trick it is...That will at least take care of the nonstarting issue. I'll still be looking for the reason that it stops unexpectedly, though. In that case, I have voltage coming from the hi and lo res parts of the opti, but no voltage at the fuel pump and no spark. It does crank, though.
That's good to know, for future repairs. Thanks.
This helps a lot. Thanks, Steveo. Time to go remind myself how little I know.
I took it out to try to datalog. I went about 200' and quit. That should be on the log. I went maybe another 3/4 mile and it quit again. Still while logging.
I noticed that while cranking, it does not show anything for injector pulse width. It did, however, see TPS movement.
Honestly sounds like it could be VATS.
Fuel pump and starter are both controlled by CCM. If VATS is the cause of the failure, your datalog will fail (CCM won't shut up and thus you'll get garbage data) and the SECURITY light will come on solid when you try to turn the key to the 'start' position.
Fuel pump has a backup, however, in that it can bypass the CCM-controlled relay if the engine has sufficient oil pressure. This prevents a CCM failure from killing the engine while the engine is already running. Of course, since the starter is controlled by the CCM it also means you can't build oil pressure that way until the VATS signal to the CCM is overridden with that resistor.
No spark means no coil firing. No injector pulse means no commanded injector. The latter could definitely be VATS. I don't recall spark being affected by VATS; I'm pretty sure all the documentation says the PCM only kills fuel, not spark.
1990 Corvette (Manual)
1994 Corvette (Automatic)
1995 Corvette (Manual)
When it was idling, the maf section went red from a low grams per second reading quite often. It didn't go very low, just enough to trip the red.
The log said that the car was at maybe 1300 rpm when it quit. I noticed that for just a fraction of a second before it quit, it read 5300 rpm. Then nothing. I'll look to see if I can find anything else.
When it's not running, it shows 3188 idle target rpm. It read the same when I turned it off with the key. I guess that's what it does when it's not running.
Last edited by Gasnmyveins; 07-03-2023 at 09:26 PM.
graph your rpm
huge spikes and drop outs that could not possibly be actually engine speed fluctuations are usually optispark issues
the maf can definitely go into the red at a low idle, the "warning" airflow set up for that was pretty arbitrary
I've noticed that the rpm never rose much above 1300 rpm, even though I was probably at 2500 before i shifted gears.
I remember revving it after i got it to start after the first time it quit. I'll see if it registered.
Also, the O2 numbers fluctuate wildly. From nearly 1000 down to 80 or so. The sensors aren't very even, either.
It did see both revs. I'm not sure how accurate it was the rest if the time, because I had to drive so slowly in my area.
o2 sensors fluctuating wildly is usually a good thing
What? Seriously?
google "o2 sensor voltage" or something
No, I believe you. It just sounds so counterintuitive.
no really you gotta google and read and figure out how various sensors work or you will be crippled trying to understand stuff
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