When the automobile engine runs at a medium speed, there is a regular "shooting sound" at the exhaust pipe. At this time, the throttle opening decreases and the engine speed decreases, which makes the automobile engine run at a low speed and the shooting sound at the exhaust pipe is loud.

This kind of flapping sound of automobile engine is generally caused by serious erosion of exhaust valve or exhaust valve working face and loose valve seat ring. After these conditions occur in the engine, when the exhaust valve is closed during operation, the closed exhaust valve cannot completely cut off the exhaust passage.

During the power stroke, when the gas in the cylinder pushes the piston downward, a part of mixed gas will be discharged from the gap, and a strong and regular sound will be made at the exhaust pipe, which is called slapping sound.

Extended data

When repairing the abnormal sound fault of engine exhaust pipe, the faulty cylinder should be determined by measuring the cylinder pressure or breaking the cylinder. Then repair and grind the exhaust valve or seat ring according to the cause of shooting failure, and pay attention to timely maintenance when this failure occurs, so as to avoid serious accidents and greater losses caused by valve seat ring falling off.

Another situation is that the ignition time is too early or the cylinder is wrong, the mixture is too rich and the oil level is too high. Principle: Some gasoline will only burn when it is about to be discharged, so it will only burn in the exhaust pipe, and it will be discharged from the exhaust pipe with the exhaust gas flow, forming a shooting sound.