What causes increased exhaust pipe vibration frequency?

[VonLorenzo]

Reasons for increased exhaust pipe vibration frequency: 1. Intake manifold or various valve leaks - incorrect air intake can cause excessively rich or lean air-fuel mixture, leading to abnormal engine combustion; 2. Excessive carbon deposits or dirt on throttle body and surrounding intake passages - changes in air passage cross-sectional area prevent the control unit from precisely regulating idle air intake; 3. Incorrect air intake measurement - the control unit receives erroneous signals from air flow sensors and issues wrong commands, resulting in inaccurate idle air intake, abnormal mixture concentration, and consequently abnormal engine combustion, which are indirect causes of unstable idle.