Reasons for Abnormal Noises in Car Engines?

[Nigel]

There are several reasons for abnormal noises in car engines: 1. Aging or loosening of engine mounts: The rubber blocks between the engine and the frame may age or loosen, causing the engine to shake and produce abnormal noises. 2. Engine misfire noise: This occurs when one or more cylinders in the engine are not functioning properly, leading to abnormal noises. 3. "Piston slap" noise: Poor lubrication and excessive wear between the piston and cylinder wall can cause the clearance tolerance to exceed the normal range. When the engine runs, the piston skirt impacts the cylinder wall, producing noise. 4. Overly rich air-fuel mixture: When the engine's air-fuel mixture is too rich, the engine may be difficult to start, experience poor acceleration after starting, run unevenly, and produce abnormal noises. 5. Timing gear noise: After prolonged use, gears may become excessively worn, and in severe cases, the gear teeth may even wear down completely. Loose meshing between gears can also produce abnormal noises.