What is the reason for the rattling sound of the engine?

[AniyahLee]

The causes of the rattling sound from the engine are as follows: 1. Engine misfire: Engine misfire mainly refers to one or more cylinders of the engine not working properly. It is usually manifested as intermittent exhaust flow from the car, severe shaking of the exhaust pipe, and a clear "popping" or thumping sound from the engine. This phenomenon is often related to faults in the ignition coil. 2. Overly rich air-fuel mixture: When the engine's air-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, popping sounds from the engine, occasional backfiring, reduced engine power, and increased fuel consumption. These issues are often related to carbon deposits or clogged filters. 3. Cold start: During a cold start, the engine's lubrication is less effective, the engine oil has poor fluidity and is more viscous, leading to mechanical wear noises. Additionally, during a cold start, the coolant temperature is low, the air-fuel mixture is rich, and incomplete combustion can cause the engine to shake and produce popping sounds. This is generally considered a normal phenomenon.