Idle Air Control (IAC)
The idle air control (IAC) is an electrically operated, spring‑loaded solenoid valve that controls the amount of air bypassing the
closed throttle shutter. Signals from the ECM regulate the duty cycle for which the IAC valve remains open. The duty cycle
ranges from 0% to 100% open.
IAC Removal
1.
Remove the air box. Refer to Air Box Removal.
2.
Remove the two screws that secure the IAC to the throttle body assembly, and remove the IAC.
3. Disconnect the IAC from the engine harness.
4. Remove the bypass hose from the IAC.
a - IAC mounting screws (2)
b - Bypass hose
c - Engine harness connector
IAC Test
1.
Apply 69 kPa (10 psi) vacuum to the top port of the IAC.
2. Ensure the IAC holds the vacuum.
3. Apply 12 volts to the terminals of the IAC.
4. If the vacuum is not released when 12 volts is applied to the IAC terminals, replace the IAC.
a - 12 volts positive
b - 12 volts negative
5. Connect the DMT 2004 Digital Multimeter tool to the terminal pins of the IAC.
Service Procedures
Page 3C-24 © 2018 Mercury Marine 90-8M0125265 eng NOVEMBER 2017
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