A control system and method maintains a constant engine idle speed during a
garage shift of an automatic transmission-equipped vehicle with a torque
converter. An engine control module or other processor identifies when
transmission input clutch fill occurs. The engine control module increases
engine output based on the transmission input clutch fill and before a
decrease in engine idle speed occurs. The engine control module latches a
turbine speed and a speed ratio (turbine speed/engine speed). The engine
control module declares transmission input clutch fill if the latched
turbine speed minus a current turbine speed is greater than the first
calibration constant or if the latched speed ratio minus a current speed
ratio is greater than the second calibration constant. The engine control
module increases the engine output after waiting a first time delay after
the transmission clutch fill.
