What Causes Engine Noise?

[LaHayden]

Engine noise may be caused by engine misfire, rich fuel mixture, or cold start. Below are detailed explanations of the related causes: 1. Engine misfire: Engine misfire mainly refers to one or more cylinders not functioning properly, typically manifested as: intermittent exhaust flow with noticeable pauses, severe shaking of the exhaust pipe, and a clear "popping" or thumping sound from the engine. This phenomenon is often closely related to ignition coil failure. 2. Rich fuel mixture: When the engine's fuel mixture is too rich, the symptoms include: difficulty starting the engine; poor acceleration after starting, uneven engine operation; black smoke from the exhaust pipe accompanied by popping sounds, sometimes backfiring; reduced engine power and increased fuel consumption. This is mostly related to carbon buildup or clogged filters. 3. Cold start: During a cold start, the engine's lubrication is less effective, the oil has poor fluidity and is more viscous, leading to mechanical wear noises. Additionally, during a cold start, the coolant temperature is lower, and the fuel mixture is richer, resulting in incomplete combustion that causes engine shaking and popping sounds. This is generally considered a normal phenomenon.