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Backfires while decelerating past 50 mph

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Backfires while decelerating past 50 mph

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Old

May 30, 2011 | 07:35 PM

#1

joamariel

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Joined: Apr 2011

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Backfires while decelerating past 50 mph

I have a 1970 F250 farm truck and it has started making this popping/backfire type noise when it decelerates after reaching 50 mph. Anyone know what that noise might be?

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Old

May 31, 2011 | 07:12 AM

#2

gfw1985

Cranky Old Guy

Joined: Mar 2008

Posts: 3,562

Likes: 6

From: Raphine, Virginia

Unburnt fuel igniting. I would suspect a small exhaust leak as one possibility. Manifold gasket or cracked exhaust manifold.

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Old

May 31, 2011 | 10:12 AM

#3

Mike G

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Joined: Nov 2002

Posts: 3,447

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From: Littleton, CO

I had an old chev that would do this when it needed a set of points replaced (also leads to unburnt fuel).
--Mike

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Old

May 31, 2011 | 11:36 PM

#4

orich

Lead Driver

Joined: Aug 2003

Posts: 7,592

Likes: 10

From: **** hole San Jose ca.

Yup sounds like points to me, also check for warn out distributor bushing. Also check for carb leaking choke pull open diaphragm making it run lean..my 2cents
orich

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Tags

400, 66, back, backfire, decelerating, deceleration, decellerating, engine, exhaust, expedition, f250, fires, ford, mph, truck

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