Is it normal for the hot engine to vibrate violently in winter?

The phenomenon you mentioned is quite common, especially in winter.

Let me talk about my own views, which may not be completely consistent with those of several masters upstairs. Please forgive me if there is anything wrong.

First, when the cold car starts, the process of rotating speed from high to low is normal;

Second, the engine is violently shaking, commonly known as knocking, which belongs to abnormal combustion; Simply put, deflagration is the abnormal pressure in the combustion chamber caused by abnormal combustion. There are cold car knocking and hot car knocking, and your situation belongs to the former;

There are many reasons for engine knocking, at least 5-6, and the master upstairs said it was one of them.

According to you, your car usually stops for a long time before it starts, and then it will knock; However, there is no knocking phenomenon during use or when the hot car is started; Plus, you said that you just had a throttle valve and a nozzle repaired in a 4S shop. Based on this, I personally think that the cause of knocking is not that a certain cylinder does not work. If a cylinder does not work, the hot car will also knock after stopping and idling.

In my personal experience, your car should be caused by excessive carbon deposition in the engine.

If there is too much carbon deposit in the engine, the gasoline sprayed by the fuel nozzle will be absorbed by a large amount of carbon deposit when the cold car is started, which will lead to too thin mixture and abnormal combustion during the cold start, resulting in jitter and even difficulty in starting; The jitter phenomenon will gradually disappear after the carbon deposit absorbs gasoline saturation; The lower the weather temperature, the greater the amount of oil required for cold start, and the greater the influence of carbon deposition on start-up.

Knocking caused by any reason will have a certain impact on the engine. Fortunately, the carbon deposit in your car is not very serious. Go and clean up the carbon deposit, and you should be fine.

(The above is purely personal.)