What Causes Abnormal Noise During Engine Idle?

[SanRicardo]

Engine idle abnormal noise causes are as follows: Balance shaft wear: The balance shaft is used to reduce vibrations generated during engine operation. If the balance shaft oil passage becomes blocked, it will increase wear on the journal and bearings, leading to abnormal noise. Connecting rod bearing wear: If the vehicle is filled with inferior engine oil, excessive sludge may form, blocking the lubrication oil passage and preventing oil from reaching components that require lubrication and cooling. This can cause wear on the camshaft, crankshaft, and connecting rod bearings, resulting in abnormal noise. Variable timing gear clearance increase: Variable valve timing can adjust according to engine speed and operating conditions, typically using hydraulic control of the camshaft timing gear's internal rotor to achieve a certain degree of advance or delay. If the internal rotor of the variable timing gear becomes stuck or the oil chamber wears, it will lead to increased clearance and abnormal noise.