timing issue

[Ohearchai]

1990 v1500 suburban 5.7 350 tbi, Changed plugs, wires, cap and rotor, disconnected the ect, adjusted timing a touch, reconnected the ect, took it for a drive, gotta a block, starting running badly, almost misfiring, actually stalled. Got back home, turned her off, started her up again, hooked up the timing light, she was 20 degrees advanced, on a whim disconnected the ect, she went right back to 0 degrees, reconnected the ect, stayed at 0 degrees. Turned her off, started her again, back to 20 dgrees advanced. what am i doing wrong.

 

[gmbellew]

timing is set to 0 with the bypass unplugged. Do not plug in the bypass with the motor running.

If it was running fine before, I’d double check whatever you touched.

 

[Smtty58]

The ECM sets timing based on input from several sensors. First set, check all grounds. Most signals are in millivolts, a dirty ground sends an incorrect signal. Then troubleshoot sensors. I assume no codes, or you would have posted that here.