Ok thanks for clearing that up about the ECU.Those are AFAIK signal outputs from the ICM to the ECU, so I doubt the ECU could affect the ignition through those connections... doubt, provided the "timing" wire was also disconnected.
Remind me: Have you absolved the ICM? And you're confident the ICM's ground through the dizzy, hold-down clamp and engine block is soild?
Regardless, you really need a guy with an oscilloscope to pay you a visit... someone who knows how to use it and also knows what he's doing. This would go oh-so-much-faster.
And yeah I can rule out the ICM itself, issue started with old dizzy, replaced the assembly with new ICM and everything, issue didn’t change one bit.
Now the grounds do make me wonder somewhat… from what I see it was missing the following grounds,
- frame to engine block
- frame to firewall(underneath heater hoses)
- firewall to back of passenger side cylinder head
Now it seems the shop only put in 1 more ground. He brought a ground from the front of the frame on the passenger side to the block, using the bolt hole for the cutout for a mechanical fuel pump(my 350 still has it cutout, even though it’s tbi)
So that takes care of the engine block ground, but there’s still no ground strap for the firewall or the back of the cylinder head. Now thinking about it, the ICM/coil would probably use the ground on the back of the head…. I wonder if it doesn’t have good ground because it needs to travel somewhat far for one…