Passat experiences intermittent shaking during cold idle, but runs smoothly when warm

[MacNevaeh]

Passat cold start shaking phenomenon is fundamentally caused by poor combustion in the cylinders. Poor combustion leads to insufficient power output, resulting in vehicle shaking. Idle shaking issues are largely related to fuel quality. Poor fuel quality not only affects the overall performance of the engine but can also cause long-term damage to the engine and shorten its service life. Therefore, it is recommended that car owners avoid using inferior fuel to save money temporarily, and refrain from blindly using higher-octane gasoline. Instead, choose the appropriate fuel grade according to the vehicle manual. Idle shaking is inevitably linked to the often-discussed topic of engine carbon deposits. If the engine has carbon buildup or excessive carbon deposits, more fuel will be absorbed by the deposits during startup, leading to insufficient combustion mixture and resulting in difficult starts or even idle shaking. Therefore, when idle shaking occurs, engine carbon deposits must be checked as a critical component.