Stalling out! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jgknowla1 · 07-01-2011, 02:01 PM

I hope someone knows what's going on with my truck. I've got an '82 C10 305/350.

Couple days ago while driving to work I noticed that the idle rpms were lower than normal at stoplights. On my way home that day, it even stalled at a light. Normal driving speeds are fine - it has fine acceleration, sounds normal, etc. So here's that info:

* When I idle, the RPMs drop slowly over the course of about a minute until it stalls.
* Choking it (manual choke) brings the RPMs back up and it idles fine.
* changed fuel filter - old one was clean inside
* changed plugs and wires
* adjusted idle screws on carb (qjet) to 2.5 turns out each
* looked for and couldn't find any vacuum leaks - tightened down carb to torque specs
* Carb was rebuilt about a year ago and has been working fine

Any ideas of where I should look? What could be doing this?

jgknowla1 · 07-01-2011, 06:50 PM

OK, I took the top off the Qjet this afternoon and cleaned it out. I also lowered the float a tiny bit since it seemed that fuel was soaking the top gasket.

I didn't see anything wrong with the carb. I put it all back together and it made no difference - still stalling out. RPMs still slowly drop in idle and then it stalls.

Anybody have any ideas?

donut · 07-02-2011, 07:28 AM

Too lean?

How much choke "fixes" it? IMO, a little choke and you may be running a little to lean. Lot of choke and you may have a vacuum leak you can't find.

It may be something simple that you can't see yet. crud in passages could do this. Also a stumbling problem I had was fixed by cleaning out a tiny piece of gasket that was touching the metering rod/jet area and causing a lean condition.

How are you adjusting the idle mixture?

Hoods69BadBowTie · 07-02-2011, 11:26 PM

Yea I agree I am thinking its to lean or you got an unknown vacuum leak! Have you checked the fuel filter in your carb I am pretty sure it would have one?

rayfinseats · 07-03-2011, 11:53 AM

Fuel pump? Vapor lock?

jgknowla1 · 07-05-2011, 08:29 AM

Hey thanks for all the replies - lean condition makes sense I think. This weekend I redid the timing and found that base timing was too far advanced by probably 8 or 10 degrees. So I set it back to what the decal says (8) and it's running and idling much better.

I don't know enough to understand why timing would make it seem like it's lean, but I guess if it's not burning the gas efficiently that it could look the same.

Anyway, I know I've got the throttle shaft vacuum leak that's so common on Qjets, and there may be more. So I'm sure vacuum leaks are contributing to the truck's tune, but I can't replace the carb just now.

The only way I know how to adjust the mixtures is with the little screws on the front of the carb. I'll drive it for a while and see if it still acts like it's lean.

Thanks guys!

Stepper562 · 07-06-2011, 01:26 AM

Advanced timing means the truck runs faster in laimans terms, sucking in more air but same fuel amount. Gotta fatten it up a bit. Slow down the idle screw a bit and throw a little more fuel into it. See if that works. If not, vacuum leak it is. I'd check for the before anything. A lot cheaper then anything else. If not a vacuum leak, replace the carb.

Good luck, let us know how you make out for future members.
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07-01-2011, 02:01 PM	#1
jgknowla1 Registered User Join Date: Mar 2010 Location: Cary, NC Posts: 48	Stalling out! I hope someone knows what's going on with my truck. I've got an '82 C10 305/350. Couple days ago while driving to work I noticed that the idle rpms were lower than normal at stoplights. On my way home that day, it even stalled at a light. Normal driving speeds are fine - it has fine acceleration, sounds normal, etc. So here's that info: * When I idle, the RPMs drop slowly over the course of about a minute until it stalls. * Choking it (manual choke) brings the RPMs back up and it idles fine. * changed fuel filter - old one was clean inside * changed plugs and wires * adjusted idle screws on carb (qjet) to 2.5 turns out each * looked for and couldn't find any vacuum leaks - tightened down carb to torque specs * Carb was rebuilt about a year ago and has been working fine Any ideas of where I should look? What could be doing this?

07-01-2011, 06:50 PM	#2
jgknowla1 Registered User Join Date: Mar 2010 Location: Cary, NC Posts: 48	Re: Stalling out! OK, I took the top off the Qjet this afternoon and cleaned it out. I also lowered the float a tiny bit since it seemed that fuel was soaking the top gasket. I didn't see anything wrong with the carb. I put it all back together and it made no difference - still stalling out. RPMs still slowly drop in idle and then it stalls. Anybody have any ideas?

07-02-2011, 07:28 AM	#3
donut Registered User Join Date: Aug 2009 Location: S.C. Posts: 1,593	Re: Stalling out! Too lean? How much choke "fixes" it? IMO, a little choke and you may be running a little to lean. Lot of choke and you may have a vacuum leak you can't find. It may be something simple that you can't see yet. crud in passages could do this. Also a stumbling problem I had was fixed by cleaning out a tiny piece of gasket that was touching the metering rod/jet area and causing a lean condition. How are you adjusting the idle mixture? __________________ '86 C-30 dually, 454/tbh400 '73 K-20 350/350/205 (sold ) I'm kinda like duct tape- no real purpose, but handy to have around.

07-02-2011, 11:26 PM	#4
Hoods69BadBowTie Chevys Kick A$$ Join Date: Jan 2005 Location: Zootown, MT Posts: 12,699	Re: Stalling out! Yea I agree I am thinking its to lean or you got an unknown vacuum leak! Have you checked the fuel filter in your carb I am pretty sure it would have one? __________________ HOODS is what I answer too -'79, '77, '88 Pickup Sold, '85 Camaro, '83 T/A, '81,'83,'90 K5 Blazer All Sold -'79 3/4 ton "Big Yellow Bananna" Lifted 4spd. 39.5 TSL Swampers, The money Pit -'86 K5 Blazer Silverado 6.2 4" lift 35"s -'95 Ext. Cab Shorty 4" Tuff Country rolling 35" M/T's -'83 Monte Carlo T-Tops. 126,500 Original Miles -LATER I would rather push a Chevy then drive a ford!!

07-03-2011, 11:53 AM	#5
rayfinseats Registered User Join Date: Dec 2010 Location: sioux city, iowa Posts: 619	Re: Stalling out! Fuel pump? Vapor lock?

07-05-2011, 08:29 AM	#6
jgknowla1 Registered User Join Date: Mar 2010 Location: Cary, NC Posts: 48	Re: Stalling out! Hey thanks for all the replies - lean condition makes sense I think. This weekend I redid the timing and found that base timing was too far advanced by probably 8 or 10 degrees. So I set it back to what the decal says (8) and it's running and idling much better. I don't know enough to understand why timing would make it seem like it's lean, but I guess if it's not burning the gas efficiently that it could look the same. Anyway, I know I've got the throttle shaft vacuum leak that's so common on Qjets, and there may be more. So I'm sure vacuum leaks are contributing to the truck's tune, but I can't replace the carb just now. The only way I know how to adjust the mixtures is with the little screws on the front of the carb. I'll drive it for a while and see if it still acts like it's lean. Thanks guys!

07-06-2011, 01:26 AM	#7
Stepper562 Registered User Join Date: Jun 2011 Location: Downey, ca Posts: 262	Re: Stalling out! Advanced timing means the truck runs faster in laimans terms, sucking in more air but same fuel amount. Gotta fatten it up a bit. Slow down the idle screw a bit and throw a little more fuel into it. See if that works. If not, vacuum leak it is. I'd check for the before anything. A lot cheaper then anything else. If not a vacuum leak, replace the carb. Good luck, let us know how you make out for future members. Posted via Mobile Device



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