What causes the Passat to shake at idle but not when accelerating?

[VanPenelope]

The reasons why the Passat shakes at idle but not when accelerating are as follows: 1. Severe carbon buildup inside the engine: This is often manifested as carbon deposits on the throttle body, fuel injectors, spark plugs, and pistons. When these carbon deposits accumulate to a certain extent, they absorb combustion heat and may even cause detonation or knocking. If the fuel injectors become clogged, it can lead to poor atomization of fuel, resulting in fuel dripping and smoke, which not only increases fuel consumption but also pollutes the environment. 2. Ignition system issues: This is usually caused by excessive carbon buildup on the spark plugs or insufficient ignition voltage, leading to misfiring. It may even result in single or multiple cylinder misfires, causing insufficient engine power and resulting in shaking. Severe shaking can put the engine in a state between stalling and firing.