What Causes Engine Shaking During Car Ignition?

[Sienna]

Engine shaking during car ignition may be attributed to the following two reasons: 1. Dirty throttle body or excessive carbon buildup in fuel injectors can cause shaking. After driving for a certain mileage, a dirty throttle body may fail to close properly or the idle speed control motor may become stuck, both of which can lead to excessively high engine idle speed. Carbon deposits generated during engine operation can also cause vehicle shaking, especially during startup when the engine shakes more noticeably than usual, sometimes even resulting in failure to start on the first attempt. 2. Worn engine mounts can also cause shaking. Vehicle shaking may sometimes be related to aging engine mounts. Engine mounts essentially serve as the engine's vibration damping system, absorbing minor vibrations during operation. If the engine mounts malfunction, these vibrations can transfer to the steering wheel and cabin, causing shaking at idle speed.