Hi, I'm new here because I don't know where else to turn. I have brought my 87 C4 TPI with 37k miles to 2 seperate old Corvette specialists and 1 scammed me and the other gave up on it after part swapping with no luck.
The Vette used to run but eventually stopped starting reliably. Here's a list of symptoms prior to bringing it to those shops:
-starts after sitting for a while (assuming the engine was flooded and dried out after time)
-ran for 2 minutes max before flooding itself out
-starter went bad and gave up on trying to figure it out myself at that time
1st shop didn't even work on it and tried charging me for diagnostics. Told them to get bent. 2nd shop fixed the starter and found a coolant leak on the intake manifold, replaced the gaskets, said the injectors were working fine along with coolant temp and replaced the spark plugs, wires, cap, rotor, ignition coil and wires and removed the smog nonsense. They had new symptoms show up (or maybe were always there and I wasn't aware) and said it was beyond their skill grade and towed my Vette back home for free. Honorable, but I would rather it ran.
New symptoms:
-cranks without starting
-leave key on engine off and the injectors randomly actuate
-after leaving key on for anywhere from 2 to 5 minutes, it starts but stalls immediately
-noticed a high frequency sound coming from my digital dash. Lessens or disappears after leaving key on. Not sure if it correlates with the random injector actuation
I've been told 3 different potential fixes and not sure where to start or how to properly diagnose them:
-bad injectors
-bad ground
-bad ECU
I have a voltmeter and tested the injectors. All of them ohm'd out within spec (17 ohms if I recall correctly). I was told the MAF could also be an issue but after reading up, I have doubts since it doesn't start at times.I bought a cheap oscilloscope and tried hooking it up to an injector but I simply don't know what I'm doing and couldn't really get a signal when cranking. I'd assume user error on that one. Anyways, I'm at a loss on what to do. Any help would be greatly appreciated and I will report back when the issue is solved whether through here or I save up enough and have the guts to take it to another shop. Thanks for taking the time to read.

 

Buy a noid light. Un plug all your injectors(so fuel is not constantly filling intake) and plug noid light into injector harness. Now you can crank it and see if noid light flashes for each injector pulse as it turns over.
You can also see those random injector pulses you mention with just the key on.
When key just on, wiggle the injector harness and see if noid light flashes. If there is a short to ground in the harness, it may be the cause for those random injector pulses.
Do you currently have spark while turning engine over ?

 

Most definitely unplug the injector leads, use a noid to see the random pulse. Then unplug the icm flat 4 wire connection. See if the pulse still occurs. If it’s still there bad 1227165 ecm. If it’s gone the icm is sending a drp to fire injectors.

 

Thank you both for the responses. I will get my hands on a noid light and test and report back later this week.