The invention relates to a system and a method for controlling torque output of an engine when a water pump coupled to the engine is switched on or off. The system according to the principles of the present disclosure includes a pump control module, an actuator control module, and a torque reserve module. The pump control module switches a water pump between on and off. The water pump circulates coolant through an engine when the water pump is on. The actuator control module controls a first actuator of the engine based on a first torque request and that controls a second actuator of the engine based on a second torque request. The torque reserve module adjusts a torque reserve before the water pump is switched on or off based on a change in engine load expected when the water pump is switched on or off. The torque reserve is a difference between the first torque request and the second torque request.