The truck is a 85 sierra with a 350 4bbl,
now the problem just started to happen about a week ago, i was driving like normal and it started to really stumble like down low and its never done this before so what i though it may be was the carb being dirty so i changed the fuel filter and used some carb cleaner seemed to run smoother but didnt make a difference so i check to see if both jets were squirting and they dont miss a beat. So i thought maybe a dead plug? changed them all and didnt make a difference so im thinking maybe its a vaccum loss not 100% i checked alot of the hoses and there arent any with big cracks but i may be wrong
any ideas? its really pissing me off leaving work going up hill its just sick
I would check the basic's first like the timing, normal visual inspection of the cap & rotor. look for corroded cap terminals or rotor firing pin burned away. I'm not sure about your definition of stumbling whether it is a miss, no power or a bad hesitation.
If the timing and secondary ignition are correct then I would look to the carb. An 85 model Q-jet MAY have a power enrichment solenoid that could be at fault. It's on the (looking in) right top with a 2 wire connector. If it's just a bad hesitation on take off you could have the carb pump going out.
Other problems with power loss could be restricted exhaust.
On a vacuum leak you would have a high idle in most cases.
well it idles fine and doesn't rev up at all so i guess it may not be a vaccum loss.
the exhaust is just a y-pipe to a glasspack so i know its not that
as for power its non existent when it stumbles it just sorta feels like it dies then comes back to life really big hesitation
Sounds like the pump in the carb is about gone. I'd just buy a kit and re-build it and put the new pump in (comes with the kit). GM used to sell the pumps buy themselves that were modified by being shorter to give a quicker pump shot for hesitation problems. But you still had to buy a top gasket and nowadays you can get a whole kit pretty cheap.
Make sure to check the timing also.
The idle passages and/or transition slots on the carb may be getting plugged up. Try a jug of fuel injector cleaner (I like Berryman's) in the gas tank before you do anything drastic. Also, you may have just got some bad gas.
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