Buick Excelle shaking on startup and having weak acceleration can be attributed to the following reasons: 1. Severe engine carbon buildup: The most common cause of car shaking is a dirty throttle body or excessive carbon deposits in the fuel injectors. When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold-start injector can be largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts and making it difficult to start. The solution is to clean the fuel system and check if the idle control valve has carbon buildup, which should also be cleaned. 2. Ignition system issues: Check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or weak spark plug firing can also lead to such symptoms. The solution is to inspect whether the spark plugs have excessive carbon buildup and replace them if necessary. 3. Unstable fuel pressure: If you have already cleaned the engine carbon deposits, cleaned the throttle body, replaced the fuel filter, and spark plugs but still notice the car 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 cause the car to shake. The solution is to check the fuel pressure and replace components if necessary. 4. Aging engine components: Car shaking can also be related to worn engine mounts. Engine mounts act as the shock absorption system for the engine, absorbing minor vibrations during operation. If the engine mounts are faulty, these vibrations can be transmitted to the steering wheel and the cabin, causing shaking at idle.
