Why does the car shake violently when just started?
2 Answers
The reasons for severe shaking when the car is just started: 1. When there is excessive carbon buildup 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. This makes starting difficult until the carbon deposits become saturated with gasoline, after which the engine starts more easily. After starting, the gasoline adsorbed on the carbon deposits is then drawn into the combustion chamber by the engine's vacuum suction, enriching the air-fuel mixture. The constantly fluctuating lean and rich air-fuel mixture causes idle shaking after a cold start. 2. For vehicles with fewer than 3 cylinders, shaking is mostly normal during operation, as 3-cylinder engines inherently vibrate more severely. For vehicles with 4 or more cylinders, if the shaking is worse than usual, check the engine compartment for any abnormalities, such as a cylinder not firing or multiple cylinders malfunctioning. 3. Sometimes insufficient tire pressure or balancing issues can cause the vehicle to shake. In such cases, carefully inspect the tire pressure and check for any abnormal tire wear.
The car shakes violently when starting up, a situation I often encounter, especially in winter. From my experience, it's mainly due to excessive carbon deposits inside the engine, leading to incomplete combustion of the air-fuel mixture. You might find it strange, but after a few years of driving, carbon deposits accumulate around the fuel injectors and throttle body, causing the engine to shake during startup. Another possible cause is aging spark plugs; if they don't ignite effectively, the engine will also run unevenly. I recommend regularly checking the spark plugs and changing the engine oil—don't wait until 100,000 kilometers to do so. Also, if the engine oil viscosity is too high, it becomes thick in cold weather, leading to insufficient lubrication during startup, which can cause shaking. Using higher-quality fuel and avoiding low-grade gasoline can help alleviate the problem. Cleaning the throttle body yourself isn't difficult either—just spray some cleaner on it. It saves money and extends the engine's lifespan. Remember to warm up the engine for a few minutes before driving off; the shaking will be significantly reduced.
