Home » Public Forums » GMCnet » Throttle won't "return"
| Throttle won't "return" [message #249930] |
Sat, 17 May 2014 14:21  |
LNelson
Messages: 335
Registered: December 2008
Location: Springfield, MO
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Just got back from a long trip, Lower MO to New Orleans to Florida panhandle back to Lower MO. Sometime between New Orleans and Panama City, I noticed my throttle was not returning to idle at stoplights. It would return to about 1400 rpm. If I shifted into neutral and jabbed the pedal, it would return to idle.
At the campsite in FL, I sprayed the linkage with lubricant. No difference on the return trip.
Do the return springs ever go bad? I had an "old car" buddy tell me to check my cruise control. Well, when I pulled into the driveway at home, I left it running and opened up the engine room.....the cruise control chain had some slack it in.
Is this a carb issue?
Any help will be appreciated.
Larry Nelson Springfield, MO
Ex GMC'er, then GM Busnut
now '77 Eleganza ARS WB0JOT
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| Re: [GMCnet] Throttle won't "return" [message #249931 is a reply to message #249930] |
Sat, 17 May 2014 14:23  |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Larry
There is a good chance that you throttle cable has stretched. You can either bend the gas pedal or something that I have suggested years ago is to take a fishing tackle split lead shot and put it on the throttle cable just under the pedal arm to take up the slack.
Emery Stora
77 Kingsley
Frederick, CO
On May 17, 2014, at 1:21 PM, Larry Nelson wrote:
> Just got back from a long trip, Lower MO to New Orleans to Florida panhandle back to Lower MO. Sometime between New Orleans and Panama City, I noticed
> my throttle was not returning to idle at stoplights. It would return to about 1400 rpm. If I shifted into neutral and jabbed the pedal, it would
> return to idle.
>
> At the campsite in FL, I sprayed the linkage with lubricant. No difference on the return trip.
>
> Do the return springs ever go bad? I had an "old car" buddy tell me to check my cruise control. Well, when I pulled into the driveway at home, I left
> it running and opened up the engine room.....the cruise control chain had some slack it in.
>
> Is this a carb issue?
>
> Any help will be appreciated.
> --
> Larry Nelson Springfield, MO
> Ex GMC'er, then GM Busnut
> now '77 Eleganza ARS WB0JOT
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| Re: Throttle won't "return" [message #249933 is a reply to message #249930] |
Sat, 17 May 2014 15:13 |
Otterwan
Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...
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The springs do wear and one might have broken. Many QJets have two springs sort of nested together, so it can be hard to tell if one broke. Easiest thing is to just remove the springs. If you wind up with more than two pieces total, you have a problem ;o)
1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
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| Re: [GMCnet] Throttle won't "return" [message #249934 is a reply to message #249931] |
Sat, 17 May 2014 15:24 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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You are going to have to determine whether it is a bind in the cable or another issue. Other issues that I can think of are:
1. Broken return spring. There is a double return spring attached to the carb. One spring is located inside tho other one. Replacement spring are available at most auto parts stores in the "Help" section. They are a very common part.
2. The cruise control chain is suppose to have a long tube over it. If it is missing some times, the chain gets caught with the throttle partly open.
3. The carb throttle shaft binding. I one transported a coach with a brand new "rebuilt" carb on it. The shaft was binding and causing a similar failure. A few shots of penetrating oil to the shaft bushing and exercising the shft took care of the problem. took care of that problem for over 2000 miles until I delivered the coach.
4. I would initially disconnect the cable from the carb and see if it has any binding in it when operated without the carb attached. If it does then lubricate or replace it. Jim K. Has them.
I would visually check the condition of the two return springs that are located on the carb and attached to the intake manifold just forward of the carb. Those things are usually old, rusted, stretched, and sometimes one of the pair is broken. Just replace them if they look bad.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Throttle won't "return" [message #249935 is a reply to message #249931] |
Sat, 17 May 2014 15:40 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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like this
http://www.gmcmhphotos.com/photos/misc/p30923-gmc-throttel-adjustment-by-emery-stora.html
erf
On Sat, May 17, 2014 at 12:23 PM, Emery Stora wrote:
> Larry
>
> There is a good chance that you throttle cable has stretched. You can
> either bend the gas pedal or something that I have suggested years ago is
> to take a fishing tackle split lead shot and put it on the throttle cable
> just under the pedal arm to take up the slack.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>
> On May 17, 2014, at 1:21 PM, Larry Nelson
> wrote:
>
>> Just got back from a long trip, Lower MO to New Orleans to Florida
> panhandle back to Lower MO. Sometime between New Orleans and Panama City, I
> noticed
>> my throttle was not returning to idle at stoplights. It would return to
> about 1400 rpm. If I shifted into neutral and jabbed the pedal, it would
>> return to idle.
>>
>> At the campsite in FL, I sprayed the linkage with lubricant. No
> difference on the return trip.
>>
>> Do the return springs ever go bad? I had an "old car" buddy tell me to
> check my cruise control. Well, when I pulled into the driveway at home, I
> left
>> it running and opened up the engine room.....the cruise control chain
> had some slack it in.
>>
>> Is this a carb issue?
>>
>> Any help will be appreciated.
>> --
>> Larry Nelson Springfield, MO
>> Ex GMC'er, then GM Busnut
>> now '77 Eleganza ARS WB0JOT
>
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Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
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| Re: [GMCnet] Throttle won't "return" [message #249936 is a reply to message #249935] |
Sat, 17 May 2014 16:08 |
Wayne
Messages: 106
Registered: August 2004
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If none of the above finds the cause then check the advance weights in the distributor. If they are sticky it will cause the exact thing you are describing.
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: [GMCnet] Throttle won't "return" [message #249957 is a reply to message #249931] |
Sat, 17 May 2014 18:52 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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emerystora wrote on Sat, 17 May 2014 13:23Larry
There is a good chance that you throttle cable has stretched. You can either bend the gas pedal or something that I have suggested years ago is to take a fishing tackle split lead shot and put it on the throttle cable just under the pedal arm to take up the slack.
Emery Stora
77 Kingsley
Frederick, CO
On May 17, 2014, at 1:21 PM, Larry Nelson wrote:
> Just got back from a long trip, Lower MO to New Orleans to Florida panhandle back to Lower MO. Sometime between New Orleans and Panama City, I noticed
> my throttle was not returning to idle at stoplights. It would return to about 1400 rpm. If I shifted into neutral and jabbed the pedal, it would
> return to idle.
>
> At the campsite in FL, I sprayed the linkage with lubricant. No difference on the return trip.
>
> Do the return springs ever go bad? I had an "old car" buddy tell me to check my cruise control. Well, when I pulled into the driveway at home, I left
> it running and opened up the engine room.....the cruise control chain had some slack it in.
>
> Is this a carb issue?
>
> Any help will be appreciated.
> --
> Larry Nelson Springfield, MO
> Ex GMC'er, then GM Busnut
> now '77 Eleganza ARS WB0JOT
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A stretched cable won't keep the throttle from returning, in fact it will result in just the opposite--the throttle won't open all the way. If you have slack in the cruise cable, obviously that isn't the issue. As the experts have mentioned, the return springs are suspect, but another culpret is the choke not fully opening. If the choke is a bit on the rich side or the fast idle rod is misadjusted, the throttle can hang up on the fast idle cam.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Throttle won't "return" [message #249963 is a reply to message #249957] |
Sat, 17 May 2014 19:03 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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While at Bean Station I took a test drive with an owner who's had his GMC
since '81. We could hardly climb the 5%-6% grade because the accelerator
moved down only about 1-1/2" when I pressed it. When I stopped, I reached
down and pulled the pedal up about 5"-6", bending the rod back to a normal
height.
The owner then drove and was astounded at the new-found power of his GMC.
Ken H.
On Sat, May 17, 2014 at 7:52 PM, Bob de Kruyff wrote:
> A stretched cable won't keep the throttle from returning, in fact it will
> result in just the opposite--the throttle won't open all the way.
...
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Throttle won't "return" [message #249966 is a reply to message #249963] |
Sat, 17 May 2014 19:12 |
scott cowden
Messages: 170
Registered: February 2004
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When checking a high idle situation with a carbureted engine I'd look closely at choke linkage and idle steps.
Has that already been mentioned? Sorry, have only Ben scanning the thread.
Scott
'74 x-glacier
Sent from my iPhone
> On May 17, 2014, at 8:04 PM, "Ken Henderson" wrote:
>
> While at Bean Station I took a test drive with an owner who's had his GMC
> since '81. We could hardly climb the 5%-6% grade because the accelerator
> moved down only about 1-1/2" when I pressed it. When I stopped, I reached
> down and pulled the pedal up about 5"-6", bending the rod back to a normal
> height.
>
> The owner then drove and was astounded at the new-found power of his GMC.
>
> Ken H.
>
>
>> On Sat, May 17, 2014 at 7:52 PM, Bob de Kruyff wrote:
>>
>> A stretched cable won't keep the throttle from returning, in fact it will
>> result in just the opposite--the throttle won't open all the way.
>
> ...
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| Re: [GMCnet] Throttle won't "return" [message #249985 is a reply to message #249963] |
Sat, 17 May 2014 21:39 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Ken Henderson wrote on Sat, 17 May 2014 19:03While at Bean Station I took a test drive with an owner who's had his GMC
since '81. We could hardly climb the 5%-6% grade because the accelerator
moved down only about 1-1/2" when I pressed it. When I stopped, I reached
down and pulled the pedal up about 5"-6", bending the rod back to a normal
height.
The owner then drove and was astounded at the new-found power of his GMC.
Ken H.
On Sat, May 17, 2014 at 7:52 PM, Bob de Kruyff wrote:
> A stretched cable won't keep the throttle from returning, in fact it will
> result in just the opposite--the throttle won't open all the way.
I have also fixed many of those for people. I am convinced that is caused by people tying to floor it and going past the normal travel. The easy was to tell if it is bent or if it is a stretched cable is to check the passing gear switch. If the switch located on the top end of the rod is not engaging, then the rod has been bent and simply pulling up on it a few inches to bend it back will fix the problem. If the passing gear switch is engaging (before bending the rod) then I would look for a stretched cable. I have never seen a stretched cable myself but I have only fixed 8 or 10 of these so I do not have a lot of expeience with them.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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