What does engine knocking mean in a car?
2 Answers
Engine knocking in a car is a fault phenomenon caused by premature ignition. In diesel vehicles, fuel is injected into the cylinder before the piston reaches the top dead center, leading to combustion while the piston continues to move upward, producing a specific sound—this is the phenomenon of engine knocking. In gasoline vehicles, high-voltage sparks are generated before the piston reaches the top dead center, igniting the air-fuel mixture and producing the same sound. Knocking is a primary form of abnormal combustion in engines, often occurring at high compression ratios. When it happens, the engine produces a high-frequency metallic knocking sound, hence it is also referred to as detonation.
When I was learning to drive at the driving school, my instructor mentioned the term 'engine knocking.' It refers to a sudden metallic knocking sound from the engine when you press the accelerator, especially noticeable during uphill climbs or acceleration. This is usually caused by abnormal fuel combustion, such as using lower-octane fuel than recommended. Poor-quality fuel can cause premature ignition of the air-fuel mixture, leading to collisions with the piston head and creating noise. Older cars are more prone to this issue due to incorrect ignition timing or excessive carbon buildup. I experienced it once—the sound was so alarming I thought my car would break down. I rushed to the repair shop, and the mechanic fixed it by adjusting the ignition system. Ignoring it long-term can severely damage engine pistons or cylinders, leading to costly overhauls. I recommend using high-quality fuel and performing regular engine maintenance to reduce carbon buildup—don’t wait until the knocking gets worse to address it.
