If anyone could help with my engine stalling issue on my 1995 Z28/M6 it would be GREATLY appreciated.
Symptoms:
Engine seems to stall randomly driving down the road like total power to the PCM is lost....does not seem to be fuel related as I would expect the engine to gradually slow down/shut off. I can still hear the fuel pump running when the shut down occurs.
My engine specs: Fresh 383 LT1/T56 (less than 1500 total miles) with MadZ28 tune, LT4 knock module, LT4 Hot Cam, mildly ported heads, MSD wires, MSD coil, new ignition module, brand new Accel Opti, MAC headers, New Denso 02 sensors.

Engine first stalled the day after I installed the LT4 Knock module in my PCM.
Engine would NOT re-start, turned out my Water Pump went bad and ruined my original opti with 265,000 (unbelievable huh ?) miles on it. Had my mechanic replace water pump with new GM unit, opti was replaced with new Accel unit, and new ignition module thrown in for good measure.
Engine started randomly stalling the day after I got it back from the mechanic.
I have tried a different PCM as well as an ignition module and this does not solve the problem. If it stalls driving down the road, if I cycle the key from off to run it immediately fires right back up (it is a stick, so the engine is being spun as long as the clutch is released) for a random amount of time. It ALWAYS fires right back up, but ONLY if I cycle the key from Run to Off back to Run; cycling it from Run to Accessory to Run does NOT re-fire the engine.
It seems almost like it "resets" something. I think it must be a coincidence that it started right after installing the LT4 knock module, as it still occurs with my other PCM that has an LT1 knock module. When I cycle the key I can clearly hear the fuel pump shut off then start back up when I go back to "run" key position.
Could this possibly be related to a MSD coil that is about 3 years old ?
Could it be related to a fuel filter issue....the fuel filter is just over a year old?
Is there a particular wire to the PCM that could be causing this ?
Battery + & - cables are tight, copper ground strap to driver's head is good.
Tried running engine in "Speed Density" mode by unplugging MAF, same stall occurs so it is not the MAF.
I have access to a GM Tech 2 Tool to monitor all engine sensors; anything I should look for ?
Could my mechanic have pinched any wires during the opti install that could cause this ?
Help/direction from Shoebox, Injuneer, or any of the other experts would be GREATLY appreciated !!!!!

 

Do your dash idiot lights go out when it quits? If so, could be ignition switch or connection to the switch related.

 

I don't recall any "wow" of the dash lights or cluster when this happens; I however will watch for it tonight once I get the Tech 2 for some testing; I want to see if I can read engine sensors after the stall; if not it could be the PCM losing power.
Some additional information:
If I put the clutch in and turn the key from run to "crank" to try to re-start the engine, that does not work either; restart only occurs if I cycle the key back to off; could this be resetting something ?
Also, two weeks ago fuel pressure tested out at 44psi.

 

The only thing I can think of it would be resetting is the position of the ignition switch.

 

Possibly intermittent functionality of the run position of the switch huh ?
How hard is is to replace the switch ?
I think I'm going to drop my car off with my mechanic to fix it once and for all !
I will have him run and drive the car for a few days to confirm it is NOT stalling.
I'm getting really frustrated with this after I just dropped 6K on a new 383.

 

No way to tell if it is your problem without some more diagnostic work, but there is a complete guide to replacing the switch on my Tech Page.

 

Shoebox: Thanks for the help !
It is greatly appreciated.
I'm going to play with a Tech 2 on my car tonight and probably drive it to my mechanic later this week for Ign. Switch replacement.