The amount of fuel injected into the engine is based on the intake, and the more intake, the more fuel injected. Throttle is to control the intake volume, which indirectly controls the injection volume. We usually step on the throttle to control the opening angle of the throttle. You see.

Mark_Shark put it in a nutshell. I think LZ should understand. In addition, if the throttle is dirty, it will lead to a larger throttle opening, which means an increase in fuel consumption and a delay in engine power output. At this time, the throttle needs to be cleaned.