New Passat high-speed body shaking may be caused by severe engine carbon deposits, ignition system issues, or unstable oil pressure. Severe Engine Carbon Deposits: The most common cause of car shaking is a dirty throttle body or excessive carbon buildup in the fuel injectors. When there is too much carbon inside the engine, the gasoline sprayed by the cold-start injector will be largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts and making the engine difficult to start. In this situation, the car can only start easily once the carbon deposits have absorbed enough gasoline. After starting, the gasoline adsorbed on the carbon deposits will be drawn into the combustion chamber by the engine's vacuum suction, making the air-fuel mixture too rich. The constantly fluctuating air-fuel mixture leads to idle shaking after a cold start. Ignition System Issues: Check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance in the ignition system or weak spark plug firing can also cause such issues. Unstable Oil Pressure: If you have already cleaned the engine carbon deposits, throttle body, replaced gaskets and spark plugs, but still notice body shaking at idle, it is recommended to visit a 4S shop to check the fuel supply pressure and the intake pressure sensor. Abnormal fuel pump pressure or incorrect readings and poor performance of the intake pressure sensor can also cause body shaking.
