Carb blues, please help asap! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Cw72gmc · 10-21-2011, 06:55 PM

So i've been having carb issues, after tuning up my truck is performing better but still having stall/hesitation/low idle issues. 72 gmc original 350 with a quadrajet carb.

Anything below 1500 is hesitant and bogs. Anything from 1200-4000 rpm feels normal does not miss or hesitate.

Truck used to idle high some days low others, now warm I am idling very rough at 400-500 rpm. firing does not smooth out until I put the pedal down quarter way. If i put the truck in gear and i'm less than 1500 it just bogs violently . it is a manual tranny.

I dont know where to start. all ignition stuff has been changed in the last two weeks, problem has gotten worse in the last two days. Also i noticed a spring from the passenger side carb sitting on the manifold, not sure where it goes?

Cw72gmc · 10-21-2011, 06:58 PM

Also, like i said it feels hesitent and weak until the pedal goes down, from the higher end of the rpm range it is actually very powerful still.

JimKshortstep4x4 · 10-21-2011, 07:30 PM

Assuming timing, plugs, distributor, wires, and vacuum advance are all good the first two items that I would check is the accelerator pump and the idle passages, (make sure neither side of the carb idle passages is plugged).

Jim

sanford66 · 10-21-2011, 10:28 PM

Quote:

Originally Posted by JimKshortstep4x4

Assuming timing, plugs, distributor, wires, and vacuum advance are all good the first two items that I would check is the accelerator pump and the idle passages, (make sure neither side of the carb idle passages is plugged).

Jim

I agree. Also check that your choke is working properly. Joseph

Wrenchbender Ret · 10-22-2011, 08:43 AM

Sounds like a bad vacuum leak. The base gasket can get wallered out on those. Make sure all unused vacuum outlets are pluged or capped. If not that it's time for a carb o-haul.

10-21-2011, 06:55 PM	#1
Cw72gmc ~Craig~ Join Date: Mar 2009 Location: Kearns Utah Posts: 169	Carb blues, please help asap! So i've been having carb issues, after tuning up my truck is performing better but still having stall/hesitation/low idle issues. 72 gmc original 350 with a quadrajet carb. Anything below 1500 is hesitant and bogs. Anything from 1200-4000 rpm feels normal does not miss or hesitate. Truck used to idle high some days low others, now warm I am idling very rough at 400-500 rpm. firing does not smooth out until I put the pedal down quarter way. If i put the truck in gear and i'm less than 1500 it just bogs violently . it is a manual tranny. I dont know where to start. all ignition stuff has been changed in the last two weeks, problem has gotten worse in the last two days. Also i noticed a spring from the passenger side carb sitting on the manifold, not sure where it goes?

10-21-2011, 06:58 PM	#2
Cw72gmc ~Craig~ Join Date: Mar 2009 Location: Kearns Utah Posts: 169	Re: Carb blues, please help asap! Also, like i said it feels hesitent and weak until the pedal goes down, from the higher end of the rpm range it is actually very powerful still.

10-21-2011, 07:30 PM	#3
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Carb blues, please help asap! Assuming timing, plugs, distributor, wires, and vacuum advance are all good the first two items that I would check is the accelerator pump and the idle passages, (make sure neither side of the carb idle passages is plugged). Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC Last edited by JimKshortstep4x4; 10-21-2011 at 07:31 PM. Reason: wording

10-22-2011, 08:43 AM	#5
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,229	Re: Carb blues, please help asap! Sounds like a bad vacuum leak. The base gasket can get wallered out on those. Make sure all unused vacuum outlets are pluged or capped. If not that it's time for a carb o-haul.



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