Abstract: A motor vehicle has a multi-speed automatic transmission and a cruise control system. A method of shift control when the cruise control system is enabled infers from a plurality of factors based on cruise control error quantities the desirability of forcing a downshift to a lower speed ratio.

Abstract: An improved powertrain control which recognizes the occurrence of positive engine torque caused by accelerator walk-in by the operator during coast-sync-coast downshift, and effectively prevents or arrests speed flare via engine torque management controls. The engine spark timing is normally not responsive to coast-sync-coast downshift conditions, however, when the occurrence of accelerator walk-in results in excessive positive engine torque likely to cause, or actually causing, engine speed flare is detected, spark retard is controlled to a predetermined value, thereby controlling the transmission input torque and allowing smooth application of the on-coming element for completion of the shift.

Abstract: A shift pattern control for a multiple speed ratio transmission wherein an inference-based control overrides the normal shift pattern to automatically achieve manual pulldown operation under conditions for which such operation would be advised and expected. The inference-based control is achieved with a fuzzy logic technique by which vehicle parameters influencing the desirability of manual pulldown operation are measured or estimated, and used to establish an aggregate measure of the overall need for engine braking and downshifting. In the preferred embodiment, the fuzzy logic parameters include vehicle speed, grade load, engine throttle position, time of braking and time of deceleration. The parameters are applied to membership functions to indicate the truthfulness of the specified conditions, and logical combinations of the truth indications are formed, weighted to reflect their criticality, and combined to form an aggregate measure of the overall need for pulldown operation.

Abstract: A throttle valve diagnostic apparatus monitors the integrity of a throttle valve position sensor in an internal combustion engine using an engine parameter indirectly related to the value position. If the absolute pressure of the air in the intake manifold associated with the throttle valve is less than a predetermined pressure for a predetermined amount of time while the position sensor indicates a valve position greater than a predetermined position, the valve position sensor is assumed to be faulty.