Popping from exhaust

[Bama720]

Alright in the mornings when my 85 720 4x4 with z24 carb is cold when letting of the gas all gears my exhaust sounds like small backfire. Kinda new to all of this. But after it's warmed up there I no problems. But sometimes when I turn the truck off afterwards it diesels but not bad enough to turn it back on and then backfires what could be the problem?

[datzenmike]

Run on is usually from an over rich mixture. The cylinder carbons up and becomes almost glowing hot. When shut off the compression alone is enough to fire the mixture. To prevent this an idle cut solenoid is used to shut off the idle mixture so the motor stalls. If it's working the motor must be getting the fuel from somewhere else.

 

Idle too high... set wrong, cable too tight, carb worn, secondary stuck, fast idle cam stuck

choke still on... choke or choke heater not working, choke heater relay not working, wire off choke heater.

carb flooding... float set wrong, dirt in needle valve, fuel pressure too high

[danfiveten]

my lz 2.2 does that all the time going down hills and stuff, just shows to me shes one powerfull bitch trying to burst out of her shell ;) lol

[ggzilla]

Yes a lot of modified engines run too rich, especially with Weber 32/36.

 

But if an engine only backfires while warming up - after it's warmed up there is no problems - then adjust the choke. If its set too tight it will run too rich until fully warmed up. The only trick is to set it when is stone cold first thing in the morning. Adjust it so it just barely closes when the throttle is opened, no more tight than that.

[smoke]

Or you could have an exhaust leak that pulls in air and makes it backfire. Might be small enough that when warm, the expansion closes it.

[Just Joel]

Mine pops on deceleration all the time. The wide band reads full lean... so I assume while I'm generally driving in a performance tuned semi rich state, small deposits of un burnt fuel will ignite in the exhaust system while decelerating in a low vacuum lifted dome state (oh yeah, I'm running su's) or at least that's what I tell myself because I can't find any other reason why it happens :p