3-30 ENGINE CONTROL SYSTEM
CONTROL MODE
BEFORE START:
The IAC valve is initialized at 70% opening position when engine is not running (Ignition switch OFF).
WHEN CRANKING:
The IAC valve is controlled to operate at approx. 50 – 100% duty.
Duty change depends on cylinder temperature.
AFTER START (FAST-IDLE FUNCTION):
The IAC valve is controlled to operate at approx. 40 – 70% duty until the timer, (set according to cylinder
temperature at cranking) expires, then decrease duty gradually to reach the set rpm at idle.
WHEN IDLING/TROLLING:
The IAC valve is controlled so that the engine speed is stable at the idling/trolling speed specified.
During this period, the IAC valve has a duty of approx. 30% but will vary slightly as idling/trolling conditions
change.
WHEN RUNNING (NORMAL OPERATION):
The IAC valve is controlled to operate at 20 – 90% duty, dependent on current engine conditions.
WHEN DECELERATING (DASH-POT EFFECT):
When the throttle valve is suddenly returned to full close and the throttle position sensor signal changes to
“fully closed”, the IAC valve operates at a controlled gradual return to idle/troll operating duty to prevent
engine stalling or unstable running.
NOTE:
Due to the limited intake air flow from the IAC passage and in order to effectively use both the “Dash-pot
effect” and “Fast-idle function”, the by-pass air screw must be adjusted to provide IAC valve operation at
approx. 30 ± 5% duty at the engine idling/trolling specification. See page 2-16 for the by-pass air screw
adjustment procedure.
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