What causes the mixture to be too rich?

There are several reasons why the engine mixture is too rich: ECU determines that the engine is in a partial load state. At this time, ECU determines the fuel injection quantity according to the air flow meter and crankshaft speed signal. At this time, the engine is idling, and the intake air is less, which leads to the mixture being too rich and the speed increasing.

When ECU receives the "rich mixture" signal fed back by oxygen sensor, it reduces the fuel injection amount and increases the opening of idle control valve, resulting in the rich mixture. Reduce the rotation speed. When the ECU receives the signal of "the mixture is too lean" fed back by the oxygen sensor, it increases the fuel injection amount, reduces the opening of the idle control valve, and makes the mixture too rich, thus increasing the speed.

Microscopically, the molecules of an ideal gas have mass but no volume, and are particles. The motion of each molecule in the gas is independent, and there is no interaction with other molecules, and it moves in a straight line at a constant speed until it hits the container wall.

The ideal gas molecules only collide with the wall, and the statistical average of the impulse per unit area exerted by the gas molecules on the wall during the collision process is expressed as the pressure of the gas macroscopically.

Macroscopically, an ideal gas is an infinitely thin gas, which obeys the equation of state of the ideal gas and Joule's law of internal energy.

Baidu encyclopedia-ideal gas