1992 4.3L Random Misfire Issues

[YoungHandyMan]

So I've been chasing this issue the past two weeks now with no solution.

I'd been experiencing a problem when summer rolls around with my truck backfiring through the TBI when it got hot, and with that weather now here I figured I would double check the timing on my truck. I went through the EST wire disconnect procedure and saw the timing was a little retarded from 0 degrees that the 4.3L is spec'd to. I set it and reconnected the EST and it had some pinging and a slight misfire.... fast forward a few days and it now has a random misfire/cutting out at idle and throttle. It's not consistent but I cannot idle with the EST connector CONNECTED or it will stall. When the EST is DISCONNECTED it purrs but still has the slight random misfire.

What I have done:
- Verified timing is at TDC, balancer doesn't seem to have slipped
- New ICM, Pickup Coil, Coil, Wires, Plugs, Cap, Rotor, now entire Distributor, new fuel pump, fuel filter (pressure good)
- Timing seems steady, so don't think chain is messed up.
- TPS looks good and smooth with voltage
- EGR, kill engine when pressed in, so I think that means it's good.
- Vacuum looks good, fluctuates with misfire, but I think it's the result, not the cause of misfire
- TBI Rebuilt
- CTS is newer and Ohm's look good according to table I found.
- Injector spray looks good

None of these things even remotely changed anything.

Any help?

Thanks everyone!

[Kudzupatch]

backfiring through the TBI when it got hot

For that to happen you have fuel being burned in the cylinder while an intake valve is open. I would be looking at a possible sticking or burned valve.