Why is there abnormal noise inside the Bora when idling?

[SanLillian]

Bora idle speed when the car has abnormal noise reasons are as follows: Piston knocking: Piston knocking is a common source of abnormal noise. Due to poor lubrication conditions, excessive wear between the piston and cylinder wall causes the clearance fit tolerance between them to exceed the normal range. When the engine is running, the piston skirt impacts the cylinder wall, producing a crisp "clanging" sound, which is usually more noticeable at idle or low speeds. Timing gear: After long-term use, coupled with improper gear clearance adjustment and poor lubrication conditions, gears may experience excessive wear. In severe cases, gear teeth may even become worn down, resulting in loose meshing between gears. This causes abnormal noise when the machine is operating. Piston pin noise: Due to excessive wear of components, the fit clearance between the piston pin and connecting rod bushing becomes too large, the fit between the connecting rod bushing and connecting rod small end bearing becomes loose, and the fit clearance between the piston pin and piston pin bore becomes excessive. This causes the piston to swing during movement, impacting the cylinder wall and generating abnormal noise.