What happens when the car throttle is dirty?

The symptom of dirty throttle is that the throttle is stuck heavily when refueling, and the speed is slow. When idling, the speed of stepping on the throttle rises slowly, and when driving, the speed of releasing the throttle drops immediately. Unclean throttle will affect the accuracy and smoothness of engine intake. The most obvious problem is that when idling, it may cause jitter or even flameout, and the fuel valve speed is not smooth.