A vehicular system including an electrical sub-system, an engine generating a first torque to drive a crankshaft, an electric machine applying a second torque to the crankshaft, and a mechanical accessory sub-system applying a third torque to the crankshaft. The vehicular system also includes a control sub-system having a processor and a tangible, non-transitory computer-readable medium, storing instructions that, when executed by the processor, cause the processor to (i) during idle operation of the vehicle, select a mode operation, of a plurality of system modes including a charge mode and a discharge mode, to stabilize a net torque being a sum of the first, second, and third torques, and (ii) control operation of at least one of the electric machine and the engine according to the selected mode.