A system and method for adjusting an engine throttle opening amount includes a slope-determining unit that determines an angle of inclination of a vehicle, a throttle request determining unit that determines a throttle request, and an engine control unit. The slope-determining unit may include a longitudinal g acceleration sensor. The engine control unit calculates a slope gain factor from the angle of inclination and compares the slope gain factor to a predetermined threshold. If the slope gain factor is greater than the predetermined threshold, the engine control unit generates a throttle command to increase the current throttle opening amount based on the throttle request and the slope gain factor. Alternatively, if the slope gain factor is less than or equal to the predetermined threshold, the engine control unit controls the throttle opening amount based on the throttle request and independently of the slope gain factor.