This study investigates experimentally Air-fuel ratio feedback control with a fuel valve in a LPG engine. The fueling valve is controlled by electronic control unit which is made with micro computer. Various control logics are employed and then PID control is adopter as a proper logic for own system and Air-fuel ratio feedback control by PID control was experimentally of various operation area with the stable control algorithm of PID control that was earned from the former experiment. On the process the experiment, determination experiment of each control part coefficient was the biggest variable among the whole result of experiment. We could know as a result of experiment that the lange of overshoot is bigger as the proportional control part os bigger integral control part is related with the delay time and coefficient of differential control part is related with the decrease of overshoot range from the experiment of various operation area we could also analyse consequently that direct fuel control in the fuel value makes more stable control status in rare operation and low load area.