Abstract: An adaptive closed loop fuel control system generates an index of maturity value which indicates the extent to which parameters which characterize an individual engine have been learned and stored for future use in a non-volatile memory. A timer produces the index of maturity value by measuring the elapsed time during which the fuel control system has successfully operated the engine at or near stoichiometry within a predetermined range of engine speed and load conditions. A backup mechanism counts the number of HEGO sensor state changes as the closed loop controller operates in an adaptive mode, setting the index of maturity to a predetermined value even when the measured adaptation time fails to indicate an adequate amount of adaptive operation.

Abstract: An electronic engine controller operates to control the phase angle of a variable position camshaft. The engine controller receives signals indicative of engine coolant temperature, aircharge temperature, throttle position, engine speed and camshaft position, and generates a camshaft position signal to a variable camshaft control actuator to alter the phase angle of the camshaft with respect to the engine crankshaft. The engine controller contains two tables which contain cam phase angles. The first table contains a plurality of values indexed by engine speed and engine aircharge and the second table contains a plurality of values indexed by engine speed and throttle position. The engine controller generates the camshaft position signal in one of three manners depending on the mode of engine operation. In a first mode of engine operation the camshaft position signal is generated as a function of engine coolant temperature and aircharge temperature.

Abstract: An electronic ignition timing system which cooperates with an adaptive closed loop fuel control system to provide more rapid heating of an exhaust catalyst by retarding the ignition tinning during colds starts only after an index of maturity value has been generated to indicate that fuel control parameters which characterize an individual engine have been adaptively learned and are available to operate the engine with a lean mixture during cold idling conditions. The index of maturity value alters the mode of operation of the fuel control mechanism to provide robust rich operation prior to adaptation and a more aggressive lean mode operation after the adaptive parameters have been developed which permit optimized operation, and alters the ignition timing to retard the spark to more rapidly heat the exhaust catalyst.

Abstract: An engine controller (12) controls an ignition system (88) and bypass throttle valve (96). An ignition timing signal is set to an initial value as a function of engine (10) operating parameters. The timing signal is retarded during cold operation to rapidly warm a catalyst converter (20) coupled to the engine exhaust (48). When the vacuum in the intake manifold (44) falls below a threshold level, the ignition timing signal is advanced beyond the initial value. The ignition timing signal is retarded back towards its initial value when the manifold vacuum exceeds the threshold value. Concurrently, the initial timing signal is controlled to achieve desired engine idle speed.

Abstract: An engine controller (12) controls engine idle speed via control of a bypass throttle valve (96) and an ignition timing system (88). The ignition system (88) also provides a retard in ignition timing during cold operation to rapidly warm a catalytic converter (20) coupled to the engine exhaust (48). When first entering the idle speed control mode, an initial throttle position corresponding to an initial desired inducted mass air flow is first provided as a function of predetermined conditions such as air conditioner status. This initial value (238, and 402-412) is corrected to prevent any decrease in idle speed which would otherwise occur as a result of the afore-mentioned retard in ignition timing.