Abstract: The invention is a method for diagnosing operation of a nonthermal plasma discharge device and a lean NOx trap disposed in the exhaust of an internal combustion engine. The method further includes reducing power to the nonthermal plasma discharge device and determining that the nonthermal plasma discharge device is operating properly when a concentration of NOx of exhaust gases exiting the lean NOx trap increases in response to reducing power to the nonthermal plasma discharge device. Additionally, the nonthermal plasma discharge device is found not to be operating when the NOx concentration remains substantially constant in response to a decrease in power supplied to the nonthermal plasma discharge device.

Abstract: A method and apparatus for controlling the operation of a “lean-burn” internal combustion engine in cooperation with an exhaust gas purification system having an emissions control device capable of alternatively storing and releasing NOx when exposed to exhaust gases that are lean and rich of stoichiometry, respectively, determines a performance impact, such as a fuel-economy benefit, of operating the engine at a selected lean or rich operating condition. The method and apparatus then enable the selected operating condition as long as such enabled operation provides further performance benefits.

Abstract: A method for maintaining clean spark plugs in a variable displacement engine in which at least one group of cylinders is disabled in response to the engine load being less than a predetermined value. A first timer determines the maximum period that the engine may be operated with the first group of cylinders being disabled. A second timer controls the period of time the previously deactivated cylinders need to be reactivated to clean the spark plugs, after being deactivated for the maximum period of time.

Abstract: A method for reducing hydrocarbon emissions exhausted from an internal combustion engine includes timing the opening and closing of valved intake and exhaust ports to overlap for a predetermined time period, and introducing at least one of a pressure decrease at the intake passage during said overlap and a pressure increase in said exhaust passage during said overlap to reduce late hydrocarbon emissions during the overlap. Preferably, a pressure transducer such as an acoustic transducer may be driven to provide an increased pressure pulse at the exhaust port during the overlap period. Alternatively, a preferred implementation of reduced pressure at the intake port includes the operation of a throttle bypass valve that reduces fluid flow to the intake port.