For the inertia supercharging valve inside the intake coupler, which conveys air from the intercooler to the engine, the washer that supports the axis of that valve does not have an appropriate shape, and therefore the washer and the surfaces it contacts may wear due to engine vibration etc., and this may cause the valve axis to be unstable, in which case the valve may interfere with the intake coupler. If such interference is ignored, high stress may occur on the valve axis, which may break, and a broken piece might be sucked into the engine. If this occurs, abnormal noise would be generated, and in the worst case, the engine could break.