Engine won't decelerate on it's own - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Melnickta · 01-11-2013, 10:21 AM

I have driven my truck a couple of times in the past several days and am experiencing this problem:

The engine cranks and initially idles fine. The problem that I’m having is that once I press on the accelerator, the truck wants to stay at that speed/rpm. Even when I want to decelerate, I have to apply the brakes, and the truck still remains at whatever rpm it was running prior to me braking.

If at all possible, I would like to attempt to fix this myself (unless it involves rebuilding a carburetor). Any ideas what this could be and what the fix is?

Any help is appreciated.

truckster · 01-11-2013, 10:29 AM

Start by making sure the return spring is attached to the carburetor. It should pull in the opposite direction of the throttle cable.

Make sure nothing is binding the throttle cable or linkage.

bonnieclyde100 · 01-11-2013, 10:30 AM

my first guess would be to see if your return spring has come loose or is broken. it should go from the carb to the intake.

**Daddy Brim** · 01-11-2013, 10:32 AM

Maybe return spring is broken, or something is binding with the linkage.

68gmsee · 01-11-2013, 10:32 AM

Post the type of carb and engine...

If it just started it could be sticky acclerator shaft. If it's been doing it, then it could be carb adjustments.

Melnickta · 01-11-2013, 10:56 AM

It's a 4 barrel Holly Carbuerator with a 350 Chevy smallblock

truckster · 01-11-2013, 11:31 AM

If the suggestions already offered don't fix it, post a pic of the linkage side of the carb.

ubtripn · 01-11-2013, 12:04 PM

Sounds dumb but it also may be the accelerator pedal. On my 68 I installed a new one and it was "getting stuck" due to the bottom of the pedal coming out of the two metal balls that are on the floor. (I was getting the same symptoms) I still can't get it to stay mounted correctly all the time but I just push the bottom back down when it happens.

Sammy · 01-11-2013, 04:29 PM

I had a similar problem with both the holley and edlebrock on another 350. The holley the problem was the auto electric choke wasn't hooked up and once the pedal was advanced it would hang open thus causing the higher RPM. Hooing up to a switched 12 volt circuit it idles fine. On the other carb the 4 mount nuts had worked loose enough for the carb to shift about a .032 of an inch to catch the rear plate and keep it open. That was on a performer intake. Rule out the springs and linkage first but check proper operation of your coke on the holley. Work the linkage to wide open n release see if everything returns to the proper position. Also Holley's web site does have a troubleshooting chart worth a look also. Good luck.

Melnickta · 01-12-2013, 06:37 PM

Had the truck looked at this morning... The carb needs rebuilt as the gummed up parts are causing the throttle not to go down. On top of that, I apparently have a burned head. I have black smoke from the right exhaust.

Had some money stuck back for a maaco scuff and spray... Looks like that isn't in the cards.

Thanks for all of the responses. Wish it could have been the easy fix.
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71swb4x4 · 01-12-2013, 06:41 PM

You can handle the carb rebuild. Take it slow. Get that done and then see if you still have the smoke problem. Then work on diagnosing that.
Just curious, how did they diagnose the "burned head"?
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Melnickta · 01-12-2013, 06:44 PM

It was a buddy of mine that is a shade tree mechanic. I believe the diagnosis was due to the smoke coming out of only one side of the exhaust.

Any tips on how to rebuild the carb? I'm not mechanical (at all) and it looks daunting to a novice.
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Sammy · 01-12-2013, 07:12 PM

Holley's web site has tons of info. Plus U tube. I think they even have a service on their site where they rebuild your core for X number of coin.

71swb4x4 · 01-12-2013, 07:20 PM

Another option is to buy a carb. It depends on what kind of carb you have. I bought a rebuilt carb for my 67 from Advance Auto and it was exactly like the stock carb. Ran great right out of the box.
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njmedic3306 · 01-12-2013, 07:37 PM

I had something like this happen the other day. I have a Summit air cleaner and the carb linkage got wedged under the bottom of the air cleaner.

71swb4x4 · 01-12-2013, 07:50 PM

Pull the carb and try cleaning up what you can see. Spray carb cleaner in there and work the throttle back and forth and see if you can get it to loosen up.
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01-11-2013, 10:21 AM	#1
Melnickta Registered User Join Date: May 2012 Location: Bluffton, SC Posts: 59	Engine won't decelerate on it's own I have driven my truck a couple of times in the past several days and am experiencing this problem: The engine cranks and initially idles fine. The problem that I’m having is that once I press on the accelerator, the truck wants to stay at that speed/rpm. Even when I want to decelerate, I have to apply the brakes, and the truck still remains at whatever rpm it was running prior to me braking. If at all possible, I would like to attempt to fix this myself (unless it involves rebuilding a carburetor). Any ideas what this could be and what the fix is? Any help is appreciated.

01-11-2013, 10:29 AM	#2
truckster Registered User Join Date: Jan 2001 Location: Orem, Utah Posts: 7,982	Re: Engine won't decelerate on it's own Start by making sure the return spring is attached to the carburetor. It should pull in the opposite direction of the throttle cable. Make sure nothing is binding the throttle cable or linkage.

01-11-2013, 10:30 AM	#3
bonnieclyde100 Registered User Join Date: Jan 2012 Location: Henderson,TX Posts: 336	Re: Engine won't decelerate on it's own my first guess would be to see if your return spring has come loose or is broken. it should go from the carb to the intake.

01-11-2013, 10:32 AM	#4
Daddy Brim Senior Member Join Date: Feb 2011 Location: Clovis Ca. Posts: 632	Re: Engine won't decelerate on it's own Maybe return spring is broken, or something is binding with the linkage. __________________ I'm sorry I called you stupid. I thought you knew already. 67 C-20 Custom Camper 68 Nova 396 it does wheelies 2005 Buick Century the one the wife drives 1989 Toyota Tercel to drive when I can't put gas in the first 2.

01-11-2013, 10:32 AM	#5
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Engine won't decelerate on it's own Post the type of carb and engine... If it just started it could be sticky acclerator shaft. If it's been doing it, then it could be carb adjustments. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...

01-11-2013, 10:56 AM	#6
Melnickta Registered User Join Date: May 2012 Location: Bluffton, SC Posts: 59	Re: Engine won't decelerate on it's own It's a 4 barrel Holly Carbuerator with a 350 Chevy smallblock

01-11-2013, 11:31 AM	#7
truckster Registered User Join Date: Jan 2001 Location: Orem, Utah Posts: 7,982	Re: Engine won't decelerate on it's own If the suggestions already offered don't fix it, post a pic of the linkage side of the carb.

01-11-2013, 12:04 PM	#8
ubtripn Registered User Join Date: Apr 2010 Location: Boise, ID Posts: 1,280	Re: Engine won't decelerate on it's own Sounds dumb but it also may be the accelerator pedal. On my 68 I installed a new one and it was "getting stuck" due to the bottom of the pedal coming out of the two metal balls that are on the floor. (I was getting the same symptoms) I still can't get it to stay mounted correctly all the time but I just push the bottom back down when it happens.

01-11-2013, 04:29 PM	#9
Sammy Registered User Join Date: Apr 2000 Location: Bonne Terre, Mo Posts: 3,005	Re: Engine won't decelerate on it's own I had a similar problem with both the holley and edlebrock on another 350. The holley the problem was the auto electric choke wasn't hooked up and once the pedal was advanced it would hang open thus causing the higher RPM. Hooing up to a switched 12 volt circuit it idles fine. On the other carb the 4 mount nuts had worked loose enough for the carb to shift about a .032 of an inch to catch the rear plate and keep it open. That was on a performer intake. Rule out the springs and linkage first but check proper operation of your coke on the holley. Work the linkage to wide open n release see if everything returns to the proper position. Also Holley's web site does have a troubleshooting chart worth a look also. Good luck. __________________ '69 Chevy Long Fleet & '71 GMC Short Step & Project "ODD BALL" "You can wash a pig, soak it in most expensive perfume. In the end it is still just a pig." ODD BALL build thread http://67-72chevytrucks.com/vboard/s...d.php?t=478629"

01-12-2013, 06:37 PM	#10
Melnickta Registered User Join Date: May 2012 Location: Bluffton, SC Posts: 59	Re: Engine won't decelerate on it's own Had the truck looked at this morning... The carb needs rebuilt as the gummed up parts are causing the throttle not to go down. On top of that, I apparently have a burned head. I have black smoke from the right exhaust. Had some money stuck back for a maaco scuff and spray... Looks like that isn't in the cards. Thanks for all of the responses. Wish it could have been the easy fix. Posted via Mobile Device

01-12-2013, 06:41 PM	#11
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	Re: Engine won't decelerate on it's own You can handle the carb rebuild. Take it slow. Get that done and then see if you still have the smoke problem. Then work on diagnosing that. Just curious, how did they diagnose the "burned head"? Posted via Mobile Device __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

01-12-2013, 06:44 PM	#12
Melnickta Registered User Join Date: May 2012 Location: Bluffton, SC Posts: 59	Re: Engine won't decelerate on it's own It was a buddy of mine that is a shade tree mechanic. I believe the diagnosis was due to the smoke coming out of only one side of the exhaust. Any tips on how to rebuild the carb? I'm not mechanical (at all) and it looks daunting to a novice. Posted via Mobile Device

01-12-2013, 07:12 PM	#13
Sammy Registered User Join Date: Apr 2000 Location: Bonne Terre, Mo Posts: 3,005	Re: Engine won't decelerate on it's own Holley's web site has tons of info. Plus U tube. I think they even have a service on their site where they rebuild your core for X number of coin. __________________ '69 Chevy Long Fleet & '71 GMC Short Step & Project "ODD BALL" "You can wash a pig, soak it in most expensive perfume. In the end it is still just a pig." ODD BALL build thread http://67-72chevytrucks.com/vboard/s...d.php?t=478629"

01-12-2013, 07:20 PM	#14
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	Re: Engine won't decelerate on it's own Another option is to buy a carb. It depends on what kind of carb you have. I bought a rebuilt carb for my 67 from Advance Auto and it was exactly like the stock carb. Ran great right out of the box. Posted via Mobile Device __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

01-12-2013, 07:37 PM	#15
njmedic3306 Registered User Join Date: Jan 2013 Location: Stanhope NJ (hour west of NYC)(also an hour from where my truck was made) Posts: 41	Re: Engine won't decelerate on it's own I had something like this happen the other day. I have a Summit air cleaner and the carb linkage got wedged under the bottom of the air cleaner.



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01-12-2013, 07:50 PM	#16
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	Re: Engine won't decelerate on it's own Pull the carb and try cleaning up what you can see. Spray carb cleaner in there and work the throttle back and forth and see if you can get it to loosen up. Posted via Mobile Device __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

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