What causes the Passat B5 to shake and fail to accelerate during cold starts?

[Teagan]

Passat B5 shaking and failing to accelerate during cold starts may be due to insufficient engine temperature, excessive engine carbon buildup, or faults in the vehicle's ignition coils or spark plugs. Insufficient engine temperature: At low temperatures, fuel atomization is poor, requiring higher ignition energy. Over time, the spark plug gap tends to widen, leading to reduced ignition energy, which affects performance and causes the vehicle to shake. Excessive engine carbon buildup: Carbon deposits can obstruct the idle air control valve or exceed the adjustable range of the idle air passage. Faults in the vehicle's ignition coils or spark plugs: This can cause a cylinder to misfire, resulting in vehicle shaking.