Jetta's cool car Pneumatic Shaking. What is the reason?

The reason of carbon deposition is the cold start, flameout or jitter of the car.

Carbon deposition generally appears on the inner wall of throttle valve, intake valve head, intake port, piston top and combustion chamber. Excessive carbon deposition will lead to insufficient air intake, difficult starting or easy flameout at idle speed. After the water temperature reaches the normal working temperature of the engine, the computer repeatedly adjusts the position of the throttle valve plate, causing the idle speed to rise and fall.

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 injected into the intake space where the intake valve head is located, and gum, wax and unburned carbon compounds are deposited in this part. The surface of carbon deposit is loose and porous. After stopping for a night or 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, and the mixture is thin and difficult to ignite. The motor is running, and the fuel entering the cylinder is enough to ignite after multiple injections. In this case, it will definitely be 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, which will make the cold start more difficult. Even if it can be barely started, it will be closed soon. Moreover, with the increase of engine temperature, the fuel in the carbon deposit evaporates and is sucked into the cylinder to participate in combustion. This part of the fuel is out of control, resulting in too much mixture and poor engine work.

Under the above circumstances, the computer detects that the ignition voltage data of a certain cylinder is abnormal, and according to the frequency of occurrence, an occasional or persistent bad ignition fault code will be generated, and the circuit will prevent the pollution of the fault lamp. When the poor ignition exceeds a certain frequency, the computer will control to cut off the fuel injection of the cylinder, resulting in cylinder shortage and serious trembling and weakness. Carbon deposition on the valve head will also lead to the reduction of intake cross-sectional area and insufficient intake air, which will also reduce engine power. Carbon deposition in the inlet leads to the change of the inlet from smooth to rough, which affects the intake airflow. Especially in the case of rapid acceleration, the intake air flow is very fast, and these rough carbon deposits produce the lag of air flow, which reduces the intake air volume and engine power.