Back-fire

The term derives from parallel experiences with early unreliable firearms or ammunition in which the explosive force was directed out at the breech instead of the muzzle.

On many small marine engines, a screen is placed over the intake of the carburetor as a flame arrestor, to prevent these flames from escaping the intake and potentially igniting fuel or fuel vapors in the enclosed sump or bilge of the boat, causing a fire or explosion.

Additionally, improperly adjusted carburetors that create a lean condition during acceleration can cause the air–fuel mixture to burn so slowly that combustion is still taking place during the exhaust stroke, and even when the intake valve opens.

In some high-performance vehicles, when a driver shifts up and lets off the accelerator, the engine has a moment of running rich.

The TVR Cerbera is an example of a car with factory-fitted sports exhausts which produce frequent backfires on engine braking.