The whine of Audi a6 engine 1 cylinder.

The cylinder is on fire, and the compression of the cylinder is insufficient.

1. In-cylinder fire: There are problems such as spark plug failure, ignition coil failure or insufficient oil supply in the cylinder, resulting in abnormal combustion and abnormal noise in the cylinder.

2. Insufficient compression of the cylinder: due to the poor seal of the cylinder and the damage of the piston ring, the cylinder can not generate enough compression force normally, resulting in abnormal noise when the engine works.