Why Does Engine Knocking Occur?
3 Answers
Engine knocking causes and solutions are as follows: 1. The selected gasoline has an excessively low octane rating or insufficient grade. Domestic gasoline octane ratings are generally lower than labeled. For example, if a car requires 92-octane or higher, the actual octane value of 92-grade gasoline may only be 90 due to domestic fuel quality issues. Insufficient octane rating will naturally cause knocking. Solution: Use gasoline with one grade higher. 2. Carbon deposits in the combustion chamber. Carbon buildup on piston tops from engine combustion increases the effective compression ratio, leading to knocking. Solution: Use cleaning additives to remove carbon deposits. 3. Poor spark plug ignition may also occur. Solution: Replace spark plugs, preferably all four simultaneously.
I've been studying car engines and found that engine knocking mainly stems from detonation issues. This is usually caused by premature ignition, such as from aging spark plugs or incorrect ignition timing, which leads to fuel exploding before the piston fully compresses it, producing a metallic knocking sound. Another common reason is using low-octane gasoline, especially during rapid acceleration or hill climbing, where unstable combustion occurs, and poor fuel quality easily triggers this phenomenon. Additionally, excessive carbon deposits in the engine can increase the compression ratio, making combustion more violent and thus worsening knocking. I recommend regularly cleaning carbon deposits and using premium gasoline and additives for prevention. When driving, maintain smooth acceleration and avoid overloading the engine. If the knocking persists, checking the ignition system or sensors can significantly reduce the risk of failure. Timely maintenance can enhance engine lifespan and efficiency.
As someone who has been repairing cars for many years, I believe that engine knocking is often caused by insufficient lubrication. When piston rings or connecting rod bearings wear out, coupled with oil that's too low, dirty, or of incorrect viscosity, increased friction results in that knocking sound. I've seen this frequently in older vehicles, primarily because owners neglect timely oil filter changes, leading to oil pump failure or sludge buildup. Compression ratio issues are also common, where excessive carbon deposits cause uneven combustion. Upon hearing knocking noises, first check oil level and quality, ensuring oil changes every 5,000 kilometers. Avoid sudden braking or prolonged high-RPM operation during daily driving to minimize mechanical wear. With proper prevention, the engine runs smoother.
