throttle sticks only while engine is running
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throttle sticks only while engine is running
1985 F350, 460, 2WD, Holley carb, not sure of model, non catalyst engine, egr and air for emissions, auto transmission.
When cold or warmed up throttle will stick. The throttle sticks at all openings.
If rpm is at 900 and you press on gas pedal throttle will stick at new rpm.
With engine off throttle does not stick at all.
Anyone ever have this issue? I searched the archives and can't find anything related.
When cold or warmed up throttle will stick. The throttle sticks at all openings.
If rpm is at 900 and you press on gas pedal throttle will stick at new rpm.
With engine off throttle does not stick at all.
Anyone ever have this issue? I searched the archives and can't find anything related.
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From: Virginia
This reminds me of a wierd problem I read about, where the body did not have a good ground, so it was using the throttle cable as a ground, and it would get hot and stick.
I assume your motor mounts are good? And the spring and cable mount are good on the end of the cable?
Here's a picture of what it should look like if it's factory.
http://www.autozone.com/images/cds/g...3d800acdd6.gif
I assume your motor mounts are good? And the spring and cable mount are good on the end of the cable?
Here's a picture of what it should look like if it's factory.
http://www.autozone.com/images/cds/g...3d800acdd6.gif
Tuned
Joined: Jan 2006
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From: Blue Ball, PA
Have you checked out the butterfly valves and bores? Are they dirty? How long since the carb has been rebuilt? Is it safe to assume you have a return spring on the throttle cable? Just a couple of questions to get more info to hopefully help you out.
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weird yes
It started after taking the batteries out and charging them.
My set up looks like the photo.
Which ground do I need to look at from the carb to the engine or the engine to the frame?
I have dual batteries and one grounds to the intake manifold and the other grounds to the AC mounting bracket.
There are two grounds on the carb (yellow wires) for solenoids I think, that are t'd into the vacuum hoses running to the recovery canister.
My set up looks like the photo.
Which ground do I need to look at from the carb to the engine or the engine to the frame?
I have dual batteries and one grounds to the intake manifold and the other grounds to the AC mounting bracket.
There are two grounds on the carb (yellow wires) for solenoids I think, that are t'd into the vacuum hoses running to the recovery canister.
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okay problem is now gone
OKay, here we go. I go out to check grounds and and vacuum hoses.
All grounds are correct, batteries to engine and engine to firewall. I didn't clean them, all vacuum lines are routed properly according to diagram.
Started truck up and what do you know, the throttle doesn't stick now.
I will wait for problem to reappear to look into further next time. Hope that it doesn't reappear.
All grounds are correct, batteries to engine and engine to firewall. I didn't clean them, all vacuum lines are routed properly according to diagram.
Started truck up and what do you know, the throttle doesn't stick now.
I will wait for problem to reappear to look into further next time. Hope that it doesn't reappear.
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answer to questions
Return spring as shown in photo.
How long since carb was rebuilt? Don't know.
I picked up the truck last weekend. It drove fine on the way home from the junk yard, 10 miles. It also didn't show this issue when I inspected it at the junk yard.
The throttle shaft doesn't show any excessive play or wobble. No vacuum leaks that I can find around base of carb or throttle shaft.
Carb has electric choke.
How long since carb was rebuilt? Don't know.
I picked up the truck last weekend. It drove fine on the way home from the junk yard, 10 miles. It also didn't show this issue when I inspected it at the junk yard.
The throttle shaft doesn't show any excessive play or wobble. No vacuum leaks that I can find around base of carb or throttle shaft.
Carb has electric choke.
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throttle is sticking again
Okay, it didn't take long to come back, but it is back.
Engine off throttle open and closes freely.
Engine running throttle opens freely but does not close, it sticks at where it is open to.
Engine off throttle open and closes freely.
Engine running throttle opens freely but does not close, it sticks at where it is open to.
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Postmaster
Joined: May 2008
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From: La Vergne, TN
sounds like your eletric choke has been screwed up maybe id say get a new carb but dang i would really wanna have a mechanic look at it i would be worried
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From: Virginia
With the engine running, take the cable off. Work the carb with the engine running. Does it stick? Work the cable with the engine running, but disconnected from the carb. Does it stick?
If you want to test the ground theory a little more just to rule it out, take a meter, and with the engine running and the cable disconnected from the carb, put one meter lead on the carb, the other lead on the metal part of the cable. If you get 12 volts, you have a problem. If you get zero or around a volt or less, then we can lay that to rest.
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thorttle shaft is binding
Removed throttle cable, with engine off, throttle does not return at all.
Throttle feels very tight when opening and closing with engine off.
Will remove carb and clean and see what happens.
If that doesn't do it, new carb.
truck cost 1k, so I can't complain if all I need is a carb.
Should there be a secondary return spring? Or is the one on the throttle cable the only return spring.
Throttle feels very tight when opening and closing with engine off.
Will remove carb and clean and see what happens.
If that doesn't do it, new carb.
truck cost 1k, so I can't complain if all I need is a carb.
Should there be a secondary return spring? Or is the one on the throttle cable the only return spring.
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the above post is incorrect. I remove the throttle cable, the throttle shaft moves freely with engine off and throttle cable disconnected.
The throttle shaft feels tight only with engine running and not with engine off.
Throttle cable is fine.
With engine running and throttle cable disconnected throttle shaft sticks at any position.
Will remove carb and see if the the screw that hold shaft is too tight or if carbon buildup is the problem.
The throttle shaft feels tight only with engine running and not with engine off.
Throttle cable is fine.
With engine running and throttle cable disconnected throttle shaft sticks at any position.
Will remove carb and see if the the screw that hold shaft is too tight or if carbon buildup is the problem.
Last edited by wifes65; Jul 21, 2008 at 11:29 PM. Reason: clear up information
Tuned
Joined: Jan 2006
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From: Blue Ball, PA
This sure is a curious problem, If everything is moving freely with the engine off and it sticks only with the engine running; I'm starting to think that it could be an electrical problem as described earlier in the post.
You've already eliminated the throttle cable, I think I'd check the grounds going to the carb (after you confirm the shaft and carbon build up) before going too much farther. A new carb may have the same problem if you have to switch over the solenoids from the old one.
You've already eliminated the throttle cable, I think I'd check the grounds going to the carb (after you confirm the shaft and carbon build up) before going too much farther. A new carb may have the same problem if you have to switch over the solenoids from the old one.
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removed carb
Removed carb, carb is good no carbon build up.
Choke may have been on wrong. Would need to see a photo of cam for choke.
Also found the cam and lever for the accel pump were sticking.
Put carb back on and vehicle wouldn't idle with choke off. I adjust idle speed to 700 after engine had warmed up.
Also removed grounds from top of carb to underneath base gasket.
Will see what happens this afternoon after engine cools off.
Choke may have been on wrong. Would need to see a photo of cam for choke.
Also found the cam and lever for the accel pump were sticking.
Put carb back on and vehicle wouldn't idle with choke off. I adjust idle speed to 700 after engine had warmed up.
Also removed grounds from top of carb to underneath base gasket.
Will see what happens this afternoon after engine cools off.
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cam on throttle shaft for accel pumpn is the problem
Does it makes any sense that there would be more pressure between the plastic cam on the throttle shaft for the accel pump with the engine running versus not running?
I put grease on it and it helped some but didn't eliminate the problem.
A second retrun spring would fix the issue.
It does have a flat spot on it. I will change it out and see what happens. Everything else on the carb checks out fine.
Timing is correct, no vacuum leaks, idles fine, accelerates fine
I put grease on it and it helped some but didn't eliminate the problem.
A second retrun spring would fix the issue.
It does have a flat spot on it. I will change it out and see what happens. Everything else on the carb checks out fine.
Timing is correct, no vacuum leaks, idles fine, accelerates fine
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problem solved
It was the cam on the throttle shaft that works the lever for the accel pump. It had a grooved flat spot.
I switch it and problem is solved.
Thanks to all of those that pitch in. And may this thread help someone else.
I switch it and problem is solved.
Thanks to all of those that pitch in. And may this thread help someone else.