What is the reason for the low-speed buzzing vibration of Audi a3?

The main reason is that the carbon deposition on the throttle, air intake and valve increases, which will absorb some gasoline when the car is cooling, and the gasoline will volatilize when the car is hot, resulting in too much mixed gas when the engine is idling, resulting in low-speed jitter.

Throttle is a controllable valve that controls air to enter the engine. There are two kinds of throttle: traditional cable throttle and electronic throttle. After the gas enters the intake pipe, it will be mixed with gasoline to form a combustible mixture, which will be burned to do work. It connects the air filter and the engine block, and is called the throat of the automobile engine.

Maintenance method of throttle valve:

Bleeding: oil will be heated and volatilized during use. The longer the use time, the higher the temperature and the stronger the volatilization. In addition, the compressed gas in the cylinder will squeeze into the crankcase through the gap of the piston ring to a certain extent, so there must be a channel for exhausting gas, otherwise the oil bottom will form positive pressure.

Negative pressure pumping: the reason why the crankcase ventilation pipe is connected with the throttle valve is the requirement of environmental protection on the one hand, and the gas is pumped out of the crankcase by using the negative pressure of intake air on the other hand. When the oily steam reaches the intake pipe and cools, the oil in it will condense on the intake and throttle, and then the carbon in the steam will also deposit on these parts. Because the air flow is the largest in the gap where the throttle valve is opened, the gap is small and the gas temperature is low, this part is the easiest to condense.

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