1986 c-10 surging problem , please help

[dwooten]

I have a 1986 c-10 silverado with a computer controled carb. I had the carb and transmission rebuilt a year ago and engine rebuilt 3 years ago. Recently it has been surging once up to speed after it is in 3rd gear.It feels like maybe the timing is being retarded or something , it runs good for about 3 seconds then bad for 3 seconds, it also has a strong fuel smell when it is surging but I cannot find any fuel leaking any where not sure if it would be the map sensor or maybe something came loose inside the carb ? Any help would be geatly appriciated

[old Rusty C10]

does it have a check engine light on?? even if it doesnt you can have the codes pulled usually for free at like autozone and that should tell you if its a sensor..
welcome to the board by the way and when ya have time post some pics!

[dwooten]

The check engine light is not on , however some time ago it came on with a code 34 which was the MAP sensor because the wires to the sensor were touching each other , I fixed the wires and the light went out , but was wondering that maybee since the wires were touching it may have damaged the sensor. I will post some pics when I get a chance , however it could use a paint job it has original paint

[grinch4om]

you could have dirt in the carb causing the float to stick, flooding over. (or leaning out) next time it does it, pullover and yank the air cleaner off(engine not running), see if the carb is dripping fuel into the intake. If it isn't, pump the throttle with your hand and look into carb for a pump shot, if nothing, float may be stuck closed. Now there may be other things like the sock on the fuel pick up in the tank dirty and colapsing, dual tanks? does switching tanks effect it? Is the fuel pump leaking out the weep hole? does the oil smell gassy? I dont think it's ignition. Can you floor the throttle and it comes out of it? Does it fall on its face when you floor it when this condition happens? these are indicators of rich or lean conditions. I'd bet its flooding over if I were a betting man.

[SnS C10]

autozone will not let you borrow their diagnostic tools anymore. Some lawsuit i guess. You have to buy the tool to use it.

[Albatrossian]

AZs tools can only read OBD II systems now anyway.. but I'm with grinch, sounds like a carb problem. See if you can borrow a older carb from a friend and try it.

[dwooten]

Originally Posted by grinch4om

you could have dirt in the carb causing the float to stick, flooding over. (or leaning out) next time it does it, pullover and yank the air cleaner off(engine not running), see if the carb is dripping fuel into the intake. If it isn't, pump the throttle with your hand and look into carb for a pump shot, if nothing, float may be stuck closed. Now there may be other things like the sock on the fuel pick up in the tank dirty and colapsing, dual tanks? does switching tanks effect it? Is the fuel pump leaking out the weep hole? does the oil smell gassy? I dont think it's ignition. Can you floor the throttle and it comes out of it? Does it fall on its face when you floor it when this condition happens? these are indicators of rich or lean conditions. I'd bet its flooding over if I were a betting man.

Thanks for the suggestions, switching tanks does not effect it, I will have to check these other things you mentioned, when I floor it it does come out of it, it mainly does it after you back off the throttle after cresting over a hill so the float sounds like a likely answer, it does fall on its face when I step on it if it is not completely warmed up but other than that it does run fine and as long as you are accelerating it runs fine