What Causes Car Shaking When Starting?

[CarolineAnn]

Automatic transmission car shaking when starting may be caused by the following reasons: 1. The throttle body is too dirty, causing uneven air intake and resulting in shaking. 2. Fuel line obstruction leads to insufficient fuel supply at low throttle, causing uneven operation of engine cylinders and shaking. 3. Abnormal transmission operation. Additional Information: 1. The most common cause of car shaking is excessive dirt on the throttle body or carbon buildup on the fuel injectors. When there is too much carbon deposit 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 it difficult to start. 2. In this situation, the car will only start easily after the carbon deposits have absorbed enough gasoline to become saturated. 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. This causes the engine's combustible mixture to alternate between lean and rich, resulting in idle shaking after a cold start.