What Does Engine Knock Mean?
4 Answers
Engine knock refers to an abnormal working condition of the engine, generally describing sudden and non-sustained vibrations in the engine cylinders caused by irregular ignition. Below is relevant information about engine knock: Principle of engine knock: When the engine inhales a mixture of fuel vapor and air, if the mixture ignites spontaneously before the compression stroke reaches the designed ignition point due to uncontrolled factors, the resulting powerful shockwave will oppose the piston's movement direction, causing engine vibrations. This phenomenon is known as engine knock. Hazards of engine knock: The main dangers of engine knock include reduced engine power, increased fuel consumption, amplified noise, diminished driving comfort, worsened emissions, and in severe cases, cylinder knocking, engine stalling, and mechanical component damage, which can lead to significant financial losses for vehicle owners.
I'm quite experienced with engine knocking - my car had this issue last month. Simply put, it's when the gasoline in the engine detonates spontaneously before the spark plug ignites it, making popping sounds like popcorn. The worst is when it happens suddenly while climbing hills - you can feel the throttle getting heavier. The mechanic said it's either caused by poor fuel quality (in my case, I cheaped out with substandard 92-octane from a small gas station) or excessive carbon buildup. Now I strictly use 95-octane fuel and add fuel system cleaner every 5,000 km - no more knocking since. Pro tip: in summer when using AC, avoid keeping RPMs constantly at 1500 - that can trigger knocking. Slightly higher revs are actually better for the engine.
I've been into car modifications for ten years, and engine knock is known as the engine killer on the track. When the piston moves downward, the residual exhaust gas temperature is too high, igniting the air-fuel mixture prematurely. When two flame fronts collide, it causes a knocking sound. The most damage is done to the piston rings and cylinder walls. My friend's car had engine knock for half a year without repair, and it ended up with a seized engine, costing 20,000 for a major overhaul. To avoid this, older cars need regular cleaning of combustion chamber carbon deposits, and turbocharged cars must use higher-octane gasoline. The other day, I helped a fellow car enthusiast diagnose engine knock and found it was caused by coolant leakage leading to excessive cylinder temperature. If the knock sensor alerts you, don't push it—get it checked immediately.
Last time I drove my dad's old Crown up the mountain, I encountered engine knocking—it sounded like metal clanking. The mechanic said the root cause was the gasoline self-igniting in the cylinders, getting ignited by high-temperature gases before the spark plugs could fire. This is more common in turbocharged cars or when using low-quality fuel. He taught me three emergency solutions: switch to manual mode and downshift to raise RPM, turn off the A/C to reduce load, and gently press the accelerator. Later, after replacing four fuel injectors and cleaning the intake valves, plus switching to 95-octane fuel, the knocking never happened again. Knocking not only wastes fuel but can also melt through the piston crown over time.
