Why does the Passat engine shake during cold start?

[ElainaMarie]

The root cause of the Passat shaking during cold start is poor combustion in the cylinders. When combustion is poor, the vehicle cannot provide sufficient power, resulting in shaking. Detailed explanations for engine shaking during cold start are as follows: 1. Excessive carbon deposits: When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold start injector is largely absorbed by the carbon deposits, leading to an overly lean air-fuel mixture during cold start and causing the engine to shake. 2. Fuel quality: Poor fuel quality not only affects the overall performance of the engine but also causes long-term damage and shortens its lifespan. Therefore, it is recommended that car owners avoid using low-quality fuel for temporary savings and not blindly use higher-octane gasoline. Instead, they should choose the appropriate fuel grade as specified in the vehicle manual.