strange high idle
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Junior User
Joined: May 2007
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From: Connecticut
strange high idle
was out running my truck yesterday on the highway when i got back to town the idle jumped up to about 2000 and wont drop 
what could cause this?
its a 351m w/holley 4bbl prior to highway driving everthing was the way its supposed to be nice idle. could it have jumped time???????
what could cause this?its a 351m w/holley 4bbl prior to highway driving everthing was the way its supposed to be nice idle. could it have jumped time???????
Fleet Mechanic
Joined: Nov 2003
Posts: 1,372
Likes: 14
From: West Cornwall, CT
I had the exact same truck as yours. Engine idle speed is controlled by the mechanical linkage to the carburator.
Pull the air cleaner off and check that the linkage allows the throttle plates to fully close.
While you are looking inspecting the carb, look for fuel leaks at the front bottom area of the carb. The accelerator pump gasket can be a leaker and will give cause gas smell and flat spots when accelerating.
This carb and the associated linkage is fairly easy to work on and to fix.
Lou Braun
Pull the air cleaner off and check that the linkage allows the throttle plates to fully close.
While you are looking inspecting the carb, look for fuel leaks at the front bottom area of the carb. The accelerator pump gasket can be a leaker and will give cause gas smell and flat spots when accelerating.
This carb and the associated linkage is fairly easy to work on and to fix.
Lou Braun
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Junior User
Joined: May 2007
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From: Connecticut
the linkage is free, dont smell gas anywhere or see any wet spots on or around carb. visually check vaccum lines to see if one blew apart but all are in good condition and connected.
also today she started blowing a lot of carbon through the exhaust and has a rough idle, almost as if it were missing
any help appreciated
87 f250 4x4 351m
also today she started blowing a lot of carbon through the exhaust and has a rough idle, almost as if it were missing
any help appreciated
87 f250 4x4 351m
Lead Driver
Joined: Feb 2003
Posts: 8,140
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From: Oak Harbor, OH
In '87 there was no 351m, so unless you swapped it in it's a 351w in HO form. If it's the factory 4bbl setup make sure your throttle and cruise cables aren't binding, then make sure you don't have any melted vacuum lines.
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Junior User
Joined: May 2007
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From: Connecticut
engine may have been swapped, dont know to much history on truck as i just bought it about a month ago,checked all vacuum lines and as said earlier all are in good condition. easy check as there are very few of them, (prev owner
took all emissions garbage of truck so engine is very clean)
prior to yesterday she ran fine
also cruise cable not hooked up to carb pedal cable is free and not binding
took all emissions garbage of truck so engine is very clean)
prior to yesterday she ran fine
also cruise cable not hooked up to carb pedal cable is free and not binding
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Junior User
Joined: May 2007
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From: Connecticut
any suggestions????????
any suggestions here? Truck is running pretty $#!%^y right now, blowing a lot of carbon through the exhaust 
no hesitation from the throttle when i get on it so i dont think its timing just very rough idle now and a lot of carbon
no hesitation from the throttle when i get on it so i dont think its timing just very rough idle now and a lot of carbon
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Lead Driver
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Junior User
Joined: May 2007
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From: Connecticut
sorry it has 6 bolts on covers (just ran out and checked)
just seems odd that this would happen all of a suddden
its got me baffled, retarded timing and no change in performance, so reset to where it was
just seems odd that this would happen all of a suddden
its got me baffled, retarded timing and no change in performance, so reset to where it was
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