What happened when the BMW 7 Series cold car started shaking and flameout?

The reason for carbon deposition is that the BMW 7 Series cold car started shaking and flameout. Carbon deposition usually occurs in the inner wall of throttle, intake head, air intake, piston top and combustion chamber. Excessive carbon deposition on the inner wall of solar terms will lead to insufficient air intake, and it is difficult to start or stop at idle speed. After the water temperature reaches the normal working temperature of the engine, the throttle valve is too wide to exceed the normal idle speed value, which causes the idle speed to rise and fall, and the computer repeatedly adjusts the position of the throttle valve plate.

In fact, it is not only the throttle valve that is the easiest to deposit carbon, but also the head of the intake valve (the end of the intake port). The gasoline injection of indirect injection engine is carried out between the intake ports where the intake valve head is located, in which colloid, wax and unburned carbon compounds are deposited. The surface of carbon deposit is loose and porous. After stopping overnight or for a long time, when the cold car is started, most of the fuel injected by the injector is absorbed by carbon deposits. The amount of fuel entering the cylinder is insufficient, so it is difficult to ignite the lean mixture.

With the operation of the engine, the fuel entering the cylinder is enough to ignite after multiple injections. In this case, it must be very difficult to start. What's more, if there is too much carbon in the head of the intake valve, the valve will not be closed tightly, and it will be more difficult to start the cold machine. Even if it can barely be started, it will be closed soon. Moreover, with the increase of engine temperature, the absorbed fuel evaporates in the carbon deposit and is sucked into the cylinder to participate in combustion. This part of the fuel is out of control, resulting in too rich mixture and poor engine operation.

Million car purchase subsidy