Onboard engine control for vehicles is disclosed herein. An example method includes determining a moving average of duty cycle periods for a power component of a vehicle for recent power load events, each of the duty cycle periods having both on-time portions and off-time portions; and when the on-time portions of the moving average are above a predetermined percentage, an engine of the vehicle remains in an on-state condition, further wherein when a current off-time period of the power component exceeds a value equal to a predetermined multiplier applied to the off-time portions, the engine is placed in an off-state condition.