What Causes Engine Vibration During Startup?

[SanValerie]

Below are the reasons for engine vibration during startup: 1. When driving, engine vibration may be caused by a dirty throttle valve or excessive carbon deposits in the fuel injector and intake manifold. In cold conditions, carbon deposits can absorb some of the fuel, and if the fuel does not completely enter the cylinder for combustion, it can lead to unstable idling and difficulty starting. 2. It may be caused by damage to the inner CV joint. If pits form on the inner wall of the CV joint where it frequently contacts the outer race of the needle roller bearing, the engine and transmission may perform a slight lateral tilting motion during rapid acceleration, changing the position of the force application point. As the CV joint rotates, this force application point continuously shifts back and forth along the axial direction, generating a force that pushes the vehicle body alternately to the left and right, creating a sensation of vibration. Below are the solutions for engine vibration during startup: 1. Replace the damaged inner CV joint or axle shaft. 2. Have the vehicle inspected and repaired at a 4S shop or professional repair facility.