Why does the speed of Wei Chai gas engine fluctuate?

The idling operation of the engine is to control the flow cross-section of the air passage beside the throttle by forward rotation or reverse rotation according to the steps of the idling stepping motor, so as to realize the functions of idling, fast idling and improving idling. By stepping on the accelerator pedal to change the throttle opening, the air intake is controlled. The engine computer determines the actual fuel injection quantity after obtaining the relevant signals such as comprehensive air pressure sensor and temperature sensor. The gasket connecting the throttle body and the intake manifold is made of paper or asbestos. If it is used for a long time or at high temperature, it will leak air, which will cause the intake pressure in the intake manifold to change constantly, and the engine computer will constantly adjust the fuel injection quantity, which will cause it to rise and fall at idle. After replacing the gasket, the idle speed is normal.