Fast engine torque control, increasing load
The fast method of control is used when the engine load changes rapidly, e.g. idle when turning the steering wheel rapidly so that the power steering pump puts a load on the engine. The increased torque requirement from the engine must then be compensated by a rapid increase in engine torque or the idling speed will drop. This fast compensation is done using previous ignition timing, giving higher torque.
After the fast compensation, ECM will gradually increase the throttle area in order to get more air mass into the engine while the ignition is retarded slightly. This allows ECM to maintain a torque reserve so that it can again perform fast compensation for changed engine loads.