What are the reasons for the vibration when releasing the brake in an automatic transmission car?
2 Answers
The reasons for the vibration when releasing the brake in an automatic transmission car can be attributed to the following 3 points: 1. Severe engine carbon deposits: The cause of car vibration is due to a dirty throttle valve or excessive carbon deposits in the fuel injector. When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold start injector will be largely absorbed by the carbon deposits; 2. Engine misfire: Engine misfire mainly refers to one or more cylinders in the engine not working properly. The symptoms include intermittent exhaust gas flow, severe shaking of the exhaust pipe, noticeable engine vibration, and sometimes accompanied by a sputtering sound; 3. Fluctuating air-fuel mixture in the engine: The combustible mixture in the engine sometimes becomes too lean or too rich, causing idle vibration after a cold start. The lower the temperature, the more fuel is required for a cold start, and carbon deposits can significantly affect the starting process.
When the automatic transmission car shakes upon releasing the brake to start, having driven automatic cars for years, the most common cause is excessive carbon buildup in the throttle body affecting smooth air intake. When releasing the brake, the engine needs to respond quickly to air demand, and if it's clogged, shaking occurs. Worn-out spark plugs can also cause unstable ignition; once I replaced them at the dealership, and the shaking disappeared. Insufficient or deteriorated transmission fluid can lead to rough shifting, especially at the moment of starting. Worn engine mount rubber pads can transmit vibrations, which I fixed once to resolve the issue. Additionally, frequent stop-and-go driving in the city exacerbates these problems; regular maintenance like throttle body cleaning and air filter replacement can help prevent them.
