Abstract: A method and apparatus for inferring and controlling the temperature of a NO.sub.x trap located downstream from a three-way catalyst that employs a temperature sensor to correct a temperature estimation model under relatively steady-state conditions to provide a more accurate estimate of NO.sub.x trap temperature and three-way catalyst temperature. In a second embodiment, the three-way catalyst also includes a temperature sensor for improving the instantaneous catalyst temperature estimation.

Abstract: A managed fuel air control system is provided that transitions between a closed loop stoichiometric A/F mode and an open loop lean A/F mode of operation. When conditions permit open loop lean operation, the engine A/F is ramped from stoichiometric to the desired lean A/F. Periodically, while operating in the open loop lean mode, the system returns to the closed loop stoichiometric mode to update an open loop correction factor used during the open loop lean mode. The time at stoichiometric is usually limited to the time it takes to correct errors in calibration data that have occurred during open loop operation. During lean operation, the adaptive corrections learned at stoichiometric A/F are applied.

Abstract: An internal combustion engine has a system, including diagnostics, for providing oxygen enriched air so as to control emissions of unburned hydrocarbons and carbon monoxide. The system includes the capability of determining whether the oxygen enrichment system is providing suitable mass flow to the engine and whether oxygen enrichment is available according to the specifications of the enrichment device.

Abstract: An intake system for a multicylinder internal combustion engine includes a manifold having inlet runners for conducting charge air into the cylinders of an engine, and at least one secondary throttle valve situated within at least one of the inlet runners. An actuator positions the secondary throttle valve, with the actuator being operated by a controller. The controller receives a sensed value from at least one engine operating parameter sensor, determines an appropriate position for the secondary throttle valve and predicts an optimum transition point at which the secondary throttle valve transitions to the appropriate position. The controller then initiates operation of the actuator at a point before the transition point such that the engine smoothly transitions between a first operating condition and a second operating condition.