backfires on decelaration ?

[351c4v71]

Hi guys,

Just got my car back from the speed shop. Car runs 100 times better.
However, I used to have backfire on acceleration (apparently due to dirty spark plugs) and now it's the opposite.
When I'm on the highway and accelerate it's fine, but when I let go of the gas, I hear small backfires.
Any idea why?

Thanks

[Chryco Psycho]

usually unburnt fuel in the exhaust igniting with oxygen let in by an exhaust leak

[dodge freak 2]

Could be a bad exhaust gasket or maybe a crack header pipe

[73restomod]

What brand of mufflers are you using? Some after market brands make deceleration louder then acceleration (Flowmasters anyone). Making popping and rich mixture backfires way more noticeable. When the throttle is closed especially on Carb equipped vehicles, while at speed, the increased vacuum pulls extra fuel thru the Carb. When the extra fuel hits hot tail pipes and oxygen it ignites. More than likely you have nothing to worry about, however I would still double check all my exhaust system bolts.

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[burdar]

Where are the mufflers located?  Do you have the exhaust dumping down before the axle or going out the back?  Having the mufflers closer to the front and just dumping down can cause loud popping sounds.  Having the mufflers farther back...by the gas tank helps with that.