Abstract: A system and a method of controlling an engine during and after a temporary fueling shut-off during idling, deceleration or a switch to auxiliary power generating device is presented. According to this method, maintaining power to the heater of an exhaust gas sensor during the temporary shut-off, and thus keeping the sensor operational shortly following resumption of fueling can eliminate a delay in closed loop air-fuel ratio control. This method provides improvements to fuel economy and emission control.

Abstract: A system and a method of controlling an engine during and after a temporary fueling shut-off during idling, deceleration or a switch to auxiliary power generating device is presented. According to this method, maintaining power to the heater of an exhaust gas sensor during the temporary shut-off, and thus keeping the sensor operational shortly following resumption of fueling can eliminate a delay in closed loop air-fuel ratio control. This method provides improvements to fuel economy and emission control.

Abstract: A nitrous oxide trap temperature control system for desulfating the trap uses and engine with some cylinders operating with lean combustion and some cylinders operating with rich combustion. The lean and rich combustion gases are combined to form an mixture which is fed to the trap to provide an exothermic reaction. The desired lean and rich air/fuel ratios of the respective lean and rich cylinders are determined based in part on the difference between the trap temperature and a desired trap temperature. The desired lean and rich air/fuel ratios of the respective lean and rich cylinders are also determined from the desired mixture air/fuel ratio entering the trap.