What Causes a Car to Shake During Acceleration?

[McAlejandro]

The reasons for a car shaking during acceleration are: 1. Issues with the ignition system, causing uneven ignition leading to shaking; 2. Problems with the fuel supply system, such as abnormal fuel pump pressure causing shaking; 3. Contaminants in the fuel intake system causing shaking; 4. Tire malfunctions causing shaking, etc. When there is excessive 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. In this situation, the car will only start easily once the carbon deposits have absorbed enough gasoline to reach saturation. After starting, the gasoline adsorbed on the carbon deposits will be drawn into the combustion chamber by the engine's vacuum suction, enriching the air-fuel mixture again. This fluctuation between lean and rich air-fuel mixtures causes the engine to idle roughly after a cold start.