It is not a complicated adjustment. It is similar to adjusting the brake calipers on a bicycle. you are not adjusting anything on the injection pump. If the knob alters the idle some, that means it is not frozen or rusted. Simply spray a little oil of Liquid Wrench on the adjusting nut loosen the nut and tighten the cable a little. It shouldn't be harder than a 2 on the difficulty scale.