What Causes Car Engine Idle Shaking That Disappears When Accelerating?
1 Answers
Idle resonance occurs when the engine's idle excitation frequency couples with the natural frequency of the steering system or vehicle body, causing vibration. When the throttle is fully engaged, the change in engine excitation frequency increases, avoiding the natural frequency points of certain parts of the transmission system or vehicle body, thus eliminating the vibration. If there's slight body sway or deviation while driving, it's usually tire-related. The primary cause could be improper wheel balance, requiring the owner to perform a four-wheel alignment and dynamic balancing promptly. If the vehicle doesn't deviate, perform tire dynamic balancing. Another more serious scenario might involve deformed steel rims, necessitating inspection at a professional repair shop. This condition typically occurs in vehicles with extended service life. Generally, when replacing new tires and rims, proper wheel balancing must be performed; otherwise, uneven weight distribution can easily cause steering wheel vibration. Body sway affects driving comfort and handling judgment. The third situation is caused by unbalanced or deformed drive shafts, usually occurring after multiple vehicle collisions with the chassis. Car vibration is also related to aging engine mounts (also called cushion pads). Engine mounts essentially serve as the engine's shock absorber system, responsible for absorbing minor vibrations during engine operation. If engine mounts are faulty, these vibrations transmit to the steering wheel and cabin, causing idle vibration.
