Why does the engine make abnormal noises?

[PeterDella]

Engine abnormal noise is caused by engine knocking. The following is extended information about knocking: 1. Detonation causes engine knocking. 2. Detonation is an abnormal combustion phenomenon in the engine. 3. Detonation occurs during the compression stroke. 4. When the engine is in the compression stroke, both the intake and exhaust valves close, and the piston moves upward. 5. The upward movement of the piston compresses the air-fuel mixture. 6. The pressure and temperature of the compressed air-fuel mixture increase. If the air-fuel mixture ignites prematurely, it causes detonation. 7. The combustion of the air-fuel mixture pushes the piston downward while it is moving upward. 8. This affects the engine's power output and fuel economy. 9. Severe detonation can lead to connecting rod deformation or piston cracking. 10. Engine detonation is caused by using inappropriate gasoline or carbon deposits in the combustion chamber.