Engine "coughs" when accelerator is floored

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Sep 6, 2016 | 08:49 PM

Dads76XLT

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Engine "coughs" when accelerator is floored

My truck runs fine day in, day out, but if I "floor it", the poor thing coughs once real bad, hesitates for a second or two, sometimes "pops" real loud inside the air cleaner, then it will take off running. Has been this way for years. What's up ya think??

1976 460 cid 4bbl original engine & carb

Sep 6, 2016 | 08:59 PM

RileyCarroll

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My truck does this some as well. Could that "popping through the air cleaner" be a backfire through the carb?
Check for vacuum leaks, it's probably vacuum leaks. Also try moving the accelerator cable up one slot closer on the flange coming from the accelerator pump.

Some carbs always do that, Mine does. I've tried everything. I guess I could try all new vacuum hoses if I wanted to, but I see no reason.

Sep 6, 2016 | 11:43 PM

Ozzie H.

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From: S.E. Louisiana;so far USA

Quote:

Originally Posted by Dads76XLT

If as originally equipped, the engine should have a model 4350 4-V carburetor. The carburetor has a secondary air valve plate at the top rear of the carburetor over the secondary throttle plates. This is to restrict the flow of air through the secondaries when the secondary throttle is opened during low engine speeds. As the engine gains speed these plates open gradually as the engine can handle the increased air flow. It is necessary for these to work properly in conjunction with the accelerator pump and the carburetor's choke. Page 24-26-1 through page 24-26-12 of vol.2 (engine) of the 1976 Ford truck shop manual describes this carburetor and how to make the adjustments. I have the exact year truck and engine; it doesn't have to do as you describe.

Sep 7, 2016 | 12:06 AM

hivoltj

Cargo Master

Joined: Apr 2010

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From: Billings, MT

Put some cough syrup in the gas tank...

Seriously though, check your accelerator pump squirter

Sep 7, 2016 | 12:15 AM

mountain dewd

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From: O-O-O-Oreilly's

Yep, take a look at the accelerator pumps function.

Sep 7, 2016 | 10:38 PM

Dads76XLT

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Ozzie,

How can I get hold of these shop manual pages??

Sep 7, 2016 | 10:44 PM

Dads76XLT

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Yes, it is a 4350 4-V carb

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Sep 8, 2016 | 12:54 AM

Ozzie H.

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From: S.E. Louisiana;so far USA

Quote:

Originally Posted by Dads76XLT

Ozzie,

How can I get hold of these shop manual pages??

There are 12 pages involved for that carburetor. If you plan on keeping the truck and you do your own work on it, you would be doing yourself a favor if you purchase a complete set of the shop manuals. There are 5 volumes in 4 books (3 & 4 are in the same book). They are available in paper versions or on CDs. Just go to eBay and search for "1976 Ford truck shop manual". You will find many. If you're only interested in having the one for the engine, it is volume 2. I have seen it sell for under $15 alone. I suppose that I could scan all 12 pages for the forum, but the tiny details probably would not show well. Getting the manual(s) would be better and less confusing.