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1981 Chevy c10 305 stalls when letting off the gas

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May 19, 2019, 11:50 PM

Post #1 of 5 (395 views)
1981 Chevy c10 305 stalls when letting off the gas Sign In

I have A 1981 Chevrolet Scottsdale with a 305 quadrajet, the truck starts and idles fine, it will idle as long as I want it to but when its put into gear and you start to drive everything seems okay until you let off of the gas pedal or press the brakes then the truck sputters and stalls, one turn of the key and it starts and idles but as soon as it's back in gear it's the same situation all over again. Replaced the fuel filter already, do I need a tuned or rebuilt carb?

Tom Greenleaf
Ultimate Carjunky / Moderator
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May 20, 2019, 12:53 AM

Post #2 of 5 (385 views)
Re: 1981 Chevy c10 305 stalls when letting off the gas Sign In

Wow - you said a lot just saying the model year '81 and word Quadrajet, quickly called a "QuadraBOG" brand new vehicles for a few years had to be tweaked around with to just move them before sold new - nightmare.
Great engine with a great (IMO) carb were butchered (IMO) to meet specs for a few years so awful hard to know just what you have. Carb would or could have been tossed a few times already or rebuilt or whole units just altered how lousy they ran - lived it.
Same today if you have one with some hindsight.
Try this: Isolate what's messing up by first since quite apparently but not clear touching brakes makes it stall. If it stalls just doing that while idling the vacuum to booster should be plugged off, isolated then see if it will quit the stalling.

Step by step isolate what is causing it to idle so well and croak when brake and or gas pedal is touched to one or the other is the reason.
Before I write a total repair novel on this set up and still be wrong find out which is the problem just like that - take brakes out of the picture is easiest.

Let's just begin there.

> There are soooo many versions of late Quads, and adjustments of them factory defeated so nobody would mess with them but were locked off at a incorrect setting was the nightmare. It's still around so was probably figured out so forget that for now see if the booster, hose to it or what is just leaking is the issue only first,


Tom Greenleaf
Ultimate Carjunky / Moderator
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May 20, 2019, 4:52 AM

Post #3 of 5 (375 views)
Re: 1981 Chevy c10 305 stalls when letting off the gas Sign In

? Please correct me if in-correct HT now. Does this even have an IAC if so it's inside carb - right? One wing nut holds on air cleaner housing the snorkel is just to pick up warm air off manifold for faster warm air inside air cleaner housing. The snorkel for metal air cleaner housing has a choke plate with diaphragm to switch from warm air in to cool air in that stuff all replaced or missing including stove off exhaust manifold.
The hose to divert air goes to the thermostatic widget clipped to bottom of metal of cleaner housing one side the other to actual intake vacuum. It's emission related so legally should all be there and working. All that can be removed and it should default to just cool air from under hood the few seconds worth of warm air is so marginally lowering raw fuel not "atomizing" quickly (evaporating) but will re-condense in cast iron intake so primary choke adjustment covers that. Front choke pull off is adjustable - it must crack open or thing will pour fuel out the tail pipe and gag on fuel. Most did!
Back: Absolutely clean all you can find with carb cleaner especially rods on side do adjust lots of what happens don't let those collect yuk and not move. Some of those in the cards for later you bend or have a screw to adjust. The nightmare is adjusting one if first all that touch that one are changed so done in order.
They work - just a nightmare as I said first,


Hammer Time
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May 20, 2019, 5:05 AM

Post #4 of 5 (370 views)
Re: 1981 Chevy c10 305 stalls when letting off the gas Sign In

You're right......... brain freeze

I deleted that post


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

May 20, 2019, 5:31 AM

Post #5 of 5 (364 views)
Re: 1981 Chevy c10 305 stalls when letting off the gas Sign In

All is fine. We both know there are so many types of late ones IDK if they rigged one on somehow for some state's requirements? NO, there is no standard all real manuals said to look for the carb # (unknown ever if correct new) then the ''GUESS ADJUSTMENTS" just cold start you got one chance a day. The rest was impossible if you didn't drive it around the block and go back time after time to get perfect.
Those details minor everyone got used to not fully stalling out hope we can at least hit what's the most wrong for that? Trying. Shops gave these to me new ran out of time can't spend 40 hours on adjusting they never did new either!


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