Abstract: Air/fuel and ignition control of engine are used to more rapidly heat-up a catalytic converter. A control system generates a fuel command for fuel delivery to the engine based upon at least an amount of air inducted into the engine. The fuel command is corrected by a correction value so that the exhaust gas mixture is shifted more closely to the preselected air/fuel ratio. Correction values are adaptively learned during warm engine operation from a feedback signal derived from an exhaust gas oxygen sensor. Initial warm correction values are stored in a reference table. At engine shut-off the difference between the warm correction values and the reference table are stored in an offset correction table. This offset correction table is then used during the next engine cold start to schedule the open-loop air/fuel ratio by using the cold adaptive table values which have been modified by the values stored in the corresponding cells of the offset correction value table.

Abstract: An engine air/fuel ratio control system maintains average engine air/fuel ratio at a desired lean air/fuel ratio during cold engine operation in order to more rapidly warm the catalytic converter. Fuel delivered to the engine is modulated with a truncated triangular wave which is truncated to minimize lean air/fuel excursions. An error signal is generated from the exhaust gas oxygen sensor output, and a proportional plus integral control responsive to the error signal generates a feedback correction value to maintain the desired air/fuel ratio. Gain of the controller is increased when the error signal indicates engine air/fuel operation leaner than a preselected air/fuel ratio to further minimize excursions in a fuel enleanment direction.