strutaeng
Full Access Member
Could be lot's of things like already pointed out.
Intake gaskets since you mentioned it happens cold. How long ago did you replace and how many miles on them? They seem to leak cold but once warmed up they swell and seal fine. The replacement was the version with the metal reinforcement plate, right?
Is the system going into closed loop? Fuel trims look okay? Is it running rich or lean when it's misfiring? O2 sensors data looks okay? Waveform looks good? You can check them by spraying some carb cleaner to induce a rich condition and temporarily unplugging a vacuum hose to induce a lean condition and watching the live data O2 sensors.
Distributers are also wear items. Same thing: how many miles on it since it was replaced? I had issues with my old 4.3 Vortec starting on damp/humid weather (actually, the darn thing didn't start, just cranked and cranked), but once it started it ran fine.
Worth doing a fuel pressure gauge test and see if it's dropping pressure. Also do an injector balance test.
Intake gaskets since you mentioned it happens cold. How long ago did you replace and how many miles on them? They seem to leak cold but once warmed up they swell and seal fine. The replacement was the version with the metal reinforcement plate, right?
Is the system going into closed loop? Fuel trims look okay? Is it running rich or lean when it's misfiring? O2 sensors data looks okay? Waveform looks good? You can check them by spraying some carb cleaner to induce a rich condition and temporarily unplugging a vacuum hose to induce a lean condition and watching the live data O2 sensors.
Distributers are also wear items. Same thing: how many miles on it since it was replaced? I had issues with my old 4.3 Vortec starting on damp/humid weather (actually, the darn thing didn't start, just cranked and cranked), but once it started it ran fine.
Worth doing a fuel pressure gauge test and see if it's dropping pressure. Also do an injector balance test.