Do they all backfire?
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Tuned
Joined: Jan 2012
Posts: 471
Likes: 1
From: Mount Vernon, KY
Do they all backfire?
I have been told that all these old trucks do this, but I wanted to check it out. I have a 75 F350 dually 4 speed with the 390. It backfires when I let off the gas for deceleration. The other older carbed truck I have backfired, but it's engine is dead now. Is this backfiring normal and can it harm anything? Thank You.
Elder User
Joined: Aug 2011
Posts: 915
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From: Sweet home Alabama
^^^^^What he said^^^^^
Are you sure its a back fire? If it is somethings wrong...Most back fires are when you accelerate from a short lean condition.
Are you sure its a back fire? If it is somethings wrong...Most back fires are when you accelerate from a short lean condition.
Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
A truck with a manual transmission reacts differently than a truck with an automatic transmission under coasting and deceleration scenarios.
When you coast or decelerate the engine acts as a brake, that's when you'll get the cackle and popping sound i.e. "backfiring".
It's just unburnt fuel igniting within the exhaust system, it's pretty normal and nothing to be concerned about, unless of course you're referring to some huge backfire out the exhaust.
When you coast or decelerate the engine acts as a brake, that's when you'll get the cackle and popping sound i.e. "backfiring".
It's just unburnt fuel igniting within the exhaust system, it's pretty normal and nothing to be concerned about, unless of course you're referring to some huge backfire out the exhaust.
Thread Starter
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Tuned
Joined: Jan 2012
Posts: 471
Likes: 1
From: Mount Vernon, KY
It is just small popping and and crackles usually unless a load is on it down hill. The other truck had major backfiring. i thought it wasn't a real concern, but i wanted to be certain. it may be a combination of the exhaust leak and usual popping because the exhaust isn't in the greatest of shape, and thanks for all the response so quickly.
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Post Fiend
Joined: Jul 2004
Posts: 8,786
Likes: 28
From: Northern California
Yes, Small quiet, almost inaudible with the windows up, popping with a manual tranny is normal, in lower gears going down hills when you "engine brake".
"Ka-blam" type explosions that sound like gunfire, tend to blow holes in your muffler, and scare the heck out of your neighbors is not.
"Ka-blam" type explosions that sound like gunfire, tend to blow holes in your muffler, and scare the heck out of your neighbors is not.
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