Stalling / backfire right after startup

[Darel]

'86 BII 5sp

Having an annoying issue with my BII. When you go and start it cold, it will start and idle fine. High idle is OK, normal idle is fine too. However if you try to drive the truck anywhere, it just won't. It will gag and sputter and misfire, and backfire too under a load. Clutch in / no load and it idles and revs fine. Only when it's got a load on it.

However, this is only for the first 5 minutes or so. Once you manage to stumble a quarter mile or so, it'll be A-OK and run fine all day long, around town and highway driving.

So far, I've replaced the IAC and the coolant temp sensor (for the ECU). When I first got the truck two years ago, I also gave it a full tuneup and replaced the distributor with a reman unit, keeping the original Ford module because the generic module that came with the reman dizzy was bad.

I will also note, sometimes I get some gray/black smoke from the exhaust. Like, at first start, and when it's sitting idling for a long time - for instance, when I was charging up the A/C and it basically sat in my driveway idling for about two hours.

Any thoughts?

Thanks,
Darel

 

[franklin2]

I would check the fuel pressure when it's acting up.

 

[RonD]

Revisit base spark timing
With SPOUT unplugged warm engine, base timing should be 10 or 12deg BTDC most prefer 12deg BTDC
With SPOUT plugged back in it should show about 22deg BTDC at warm idle

Spark timing issue will certainly cause your symptoms as "richer" mix burns faster so spark has to be sooner
Cold start is richer mix, a Choke mode, so spark timing needs that change

TFI can only do RPM spark timing, weights and springs in a distributor
The computer is what sets the LOAD spark timing, thats what the SPOUT(SPark OUT) wire is for, to change spark timing based on fuel mix(rich/lean) and LOAD

 

[Darel]

Revisit base spark timing
With SPOUT unplugged warm engine, base timing should be 10 or 12deg BTDC most prefer 12deg BTDC
With SPOUT plugged back in it should show about 22deg BTDC at warm idle

Spark timing issue will certainly cause your symptoms as "richer" mix burns faster so spark has to be sooner
Cold start is richer mix, a Choke mode, so spark timing needs that change

TFI can only do RPM spark timing, weights and springs in a distributor
The computer is what sets the LOAD spark timing, thats what the SPOUT(SPark OUT) wire is for, to change spark timing based on fuel mix(rich/lean) and LOAD

Thanks Ron. I did set the timing originally as you describe but I'll check it again and report back. Yeah it always stumbled pretty bad but as soon as I heard it backfiring that's where my head went too.