Hello!

[steveo]

your power wiring sounds good.

your 'sensor grounds' are grounds for the sensors themselves, they're provided by the ECM and noise filtered or referenced or whatever. they don't connect to chassis ground. don't use them as a ground except for with sensors as intended (in all seriousness, seen that fry an ecm)

in a factory configuration; two of the ECM grounds end up at the coil 'stud' (red 18 and blue 1), and the other two end up on the passenger side engine block (red pin 2 and grey pin 32). i imagine the block ones are the low noise, due to distance from the coil, and the coil ones are for high load? who knows.

i've grounded them all to a common ground block on my car, then the ground block to the accessory bracket with welding cable. never noticed a difference. my car runs perfect and all my signalling seems clean.

[steveo]

i wonder what's goin on? this has me scratching my head. very interested to see what it ends up being.

if a loose wire isn't getting yanked, maybe something ignition power related is hitting ground?

i can't see anything but physical wiring faults causing the ecm to just shut right the hell down during WOT events.

i'd say maybe try flashing a new bin or something, though, in case something horrific is going on there... but i also don't recommend flashing your ecm if you have suspicious wiring shit going on.

[Dukes164]

I think ill try changing the grounding location to the block and maybe adding another strap. Would it be a possibility that the single wire that's supporting the other 4 grounds is being overloaded? The single wire is no larger in diameter then the wires going into it. It appears to all be 16 gauge wire.

I've actually flashed the pcm and pulled tunes out of quite a few times back when i first started troubleshooting. Hasn't died yet!

[steveo]

Would it be a possibility that the single wire that's supporting the other 4 grounds is being overloaded?

it's definitely possible, but WOT doesn't really stress the electrical system much more than regular operation, so if it was a ground issue you'd figure you'd have trouble in other operating conditions.

[Dukes164]

Well I was given a tip to talk to a local guy named Ellis that is supposed to be really good with lt1's and it turns out hes been trying to figure out whats wrong with this stupid car too! The previous owner had been bringing it to him and actually still owes him $300 bucks. Anyway this cars had the problem since day one and Ellis saw the same event of the PCM shutting down. Apparently the PO had taken the car back to the guy that either made the harness or just installed it and he was told that everything is wired fine and everything is working correctly.

I double checked all the pins on the PCM connectors just to make sure nothing major was missing(didnt trace any wires). Only thing I found was that the tach output wire wasnt there yet my tach still works (have to investigate that).

[Dukes164]

Borrowed a PCM from a friend today, didn't fix the problem...

[steveo]

these pcms don't really have failures like that, but still good to try.

tach output is filtered, probably your tach is spliced to coil negative, which is acceptable.

this is definitely a fundamental electrical issue.

im still thinking something is gettin' yanked at WOT. i can't correlate it to anything else.

other ideas...

give it a couple good hard stabs of throttle as someone is watching under the hood

unhook your alternator positive and do a wot run

add a chassis to ecm ground

jump positive power to coil positive (bypass ignition switch and everything)

[Dukes164]

these pcms don't really have failures like that, but still good to try.

tach output is filtered, probably your tach is spliced to coil negative, which is acceptable.

this is definitely a fundamental electrical issue.

im still thinking something is gettin' yanked at WOT. i can't correlate it to anything else.

other ideas...

give it a couple good hard stabs of throttle as someone is watching under the hood

unhook your alternator positive and do a wot run

add a chassis to ecm ground

jump positive power to coil positive (bypass ignition switch and everything)

Yeah, I didn't really expect the PCM to fix the problem just had to knock another piece out of the equation. You were right about how the tach was wired.

I watched the motor while having someone rev and the motor is fricken solid it barely moves if at all, we even foot braked the clutch and it does not move. I did notice what i would call a lean pop when it was revved up.(only happened twice and I saw a nice flame come out of the intake both times).

Disconnecting the the alternator didn't do anything.

When you say to add a chassis ground do you mean a ground on the ecm box? or just adding a chassis ground to where the ecm is ground wires are grounded?

Didn't have time to put direct power on the coil today...

[Dukes164]

FIGURED IT OUT!!!!!! The hot battery wire going to the starter had 3 inches of exposed wire, arcing most likely to the header.

[steveo]

FIGURED IT OUT!!!!!! The hot battery wire going to the starter had 3 inches of exposed wire, arcing most likely to the header.

there ya go. had to be something hitting something.

[Dukes164]

there ya go. had to be something hitting something.

The thing fricken rips. Its gonna be faster then my vortec motor with a cc503 cam. Cant wait to get a good tune on it and see what it can really do. Thanks for all your help really appreciate it!