What are the causes of engine knocking?

[VonKayden]

Engine knocking is caused by: 1. The ignition angle being too advanced. An excessively early ignition causes most of the fuel-air mixture to burn while the piston is still in the compression stroke. The unburned mixture then undergoes extreme pressure and auto-ignites, resulting in knocking. 2. Excessive carbon deposits in the engine. Excessive carbon buildup in the combustion chamber not only increases the compression ratio but also creates high-temperature hot spots on the carbon deposits, leading to engine knocking. 3. Overheating of the engine. Operating the engine in excessively hot environments, which raises the intake air temperature, or poor circulation of engine coolant can cause high-temperature knocking. 4. Incorrect air-fuel ratio. An overly lean fuel-air mixture raises the combustion temperature, which in turn increases the engine temperature and makes knocking more likely.