Methods and systems are provided for an exhaust catalyst heating strategy that uses spark retard to increase an amount of heat output by an engine without a combustion stability limit. In one example, a method may include, during an engine cold start, applying an ignition spark at a timing that produces substantially zero combustion torque while maintaining an engine speed greater than a threshold speed via electric motor torque. Furthermore, an amount of heat output by the engine may be controlled by adjusting an airflow through the engine, such as by adjusting one or more of a throttle position and the engine speed.