85 Sierra: Low Engine Load Hitch

[a.graham52]

alright so heres the skinny.. 1985 sierra 1500 2x4 4.3l 4spd manual, 4bbl carb. 43k miles,

 

driving down the road lets say fallowing another car with light throttle the truck hitches real good. iv herd it described as a fishbite sensation too. press the throttle a little harder and it will smooth out alright. if i drive though the city for a while it will stop idling and ill have to run it really hard before it will start to idle again.

 

iv checked timing, its a 0-2 degrees BDC at 600ish rpm according to the sticker on the radiator support. just did intake gaskets and carb to intake gasket, replaced some vacuum lines, re-checked timing, checked the choke, checked the mechanical advance to make sure its free and moving well. sprayed carb cleaner all around the intake and vacuum lines and the engine didnt rev. also made sure the accelerator pump works good. if you put your hand over the carb and choke it off the idle comes up and smooths out pretty good. i was told that it means its running lean. im thinking i just need a carb but im trying to rule out anything i can before spending the money. also replaced ignition cap, button, plugs and wires.

 

anyone have any good advice. i know rebuilding a carb is an option but this is my primary mode of transportation and the less time its down the better. thansk for all the info you people might have.

[BrockwayMT]

Sounds like the fishbite is 'lean surge.' The carb is probably gummed up. Did you replace the filter on the front of the carb? Best guess would be the carb needs to be taken apart and cleaned.

[a.graham52]

Sounds like the fishbite is 'lean surge.' The carb is probably gummed up. Did you replace the filter on the front of the carb? Best guess would be the carb needs to be taken apart and cleaned.

 

 

i did not and this is why: under WOT the engine runs nice and smooth so im assuming that if the filter was clogged or the float stuck low/full of fuel then it would miss at higher rpms. wich it doesnt. but i also did a little research and im wundering if somones hasnt messed with the power valve adjustment. im thinking the power valve is letting the metering rods sit too low cutting off fuel under idle/cruis