Engine revs when I put it in gear
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Joined: Feb 2002
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From: Cleveland, WI USA
Engine revs when I put it in gear
78 F150 4x4 460/c6/Holley 750
I had the truck out this weekend and had a bizzare problem. With my foot on the brake and the truck in gear, the engine revs up by 200-300 RPM. Sometimes it does it in park, but only once in a while, and it never did it in reverse.
A bad brake booster was suggested so I disconnected it and plugged the vac port. It still happened. I disconnected the brake booster, tranny vac line, vac advance and plugged all the ports/hoses and it STILL does it. The only vac line that stayed connected was the PCV. All the ports on the carb are plugged, too
I even looked for weird stuff like broken motor mounts, pinched lines etc...
Anyone have any ideas on what might cause this or what else I can try to find the problem?
Thanks in advance!
Kevin K.
I had the truck out this weekend and had a bizzare problem. With my foot on the brake and the truck in gear, the engine revs up by 200-300 RPM. Sometimes it does it in park, but only once in a while, and it never did it in reverse.
A bad brake booster was suggested so I disconnected it and plugged the vac port. It still happened. I disconnected the brake booster, tranny vac line, vac advance and plugged all the ports/hoses and it STILL does it. The only vac line that stayed connected was the PCV. All the ports on the carb are plugged, too
I even looked for weird stuff like broken motor mounts, pinched lines etc...
Anyone have any ideas on what might cause this or what else I can try to find the problem?
Thanks in advance!
Kevin K.
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Joined: Aug 2004
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I spent this last weekend dealing with the same problem on my 77 f100/351W/600 Holley. Tried all the same things you did, no luck (thought it had to be the booster--but it wasn't). Hopefully somebody's solved this one before.
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From: Cleveland, WI USA
Already thought of that and no dice. I have a homemade floor shifter that goes directly to the tranny and it's nowhere near the throttle. Thanks for the reply though.
I thought maybe the motor mounts were bad causing the engine to tilt and rev the trottle, but that doesn't seem to be happening either.
Kevin K.
I thought maybe the motor mounts were bad causing the engine to tilt and rev the trottle, but that doesn't seem to be happening either.
Kevin K.
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Joined: Dec 2001
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From: Louisville,Ky.
Something has to be moving. If the linkage is adjusted too tight, a small amount of engine movement will cause the linkage to move and open the accelerator.
Tranny mount perhaps? It will let the tailshaft rise which tilts the engine forward and will allow the linkage to pull on the carb.
Tranny mount perhaps? It will let the tailshaft rise which tilts the engine forward and will allow the linkage to pull on the carb.
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From: west central florida
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Joined: Feb 2002
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From: Cleveland, WI USA
I disconnected the linkage last night and it seemed to solve the problem. I loosened it up and reconnected it and all seems ok. Since it's an intermittent problem, I can't be sure it's fixed until I do a full scale off-road test.
Thanks for the suggestions all!
Kevin K.
Thanks for the suggestions all!
Kevin K.
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From: North Carolina
Originally Posted by Mil1ion
Make sure you have two return springs on that accelerator linkage 
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Joined: Jul 2003
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From: okc
i only have one on my Holley, but the carb itself also has a really good spring on the throttle rod, so i guess i technically have 2...i consider the long spring the backup spring, since the carb really dont need it to close properly, but i would never think of running without it....