What Causes Abnormal Noise During Engine Idling?

[SanAva]

Engine idling with abnormal noise can be attributed to the following reasons: 1. Excessive carbon deposits: When there is too much carbon buildup on the throttle body, fuel injectors, or intake manifold, or when excessive carbon deposits accumulate inside the engine, the gasoline injected by the cold start injector can be largely absorbed by the carbon deposits. This results in an overly lean air-fuel mixture during cold starts, causing engine vibration. 2. Low cylinder pressure: After prolonged use of the engine, the gap between each cylinder liner and piston may become inconsistent. During cold starts, without proper lubrication from engine oil, cylinders with larger gaps are prone to leaking a certain amount of high-temperature gas from the gaps. This reduces power output, leading to low oil pressure and cylinder pressure, which in turn causes insufficient power and engine vibration. 3. Faulty ignition coil: If the ignition coil malfunctions, such as cracking and leaking electricity, it can result in insufficient or lack of spark plug ignition capability. Consequently, the air-fuel mixture in that cylinder will not combust properly, leading to engine misfire, difficulty starting, and acceleration vibration.