The Idle Air Control (IAC) system is used to stabilize idle speed during cold engine and after warm-up operations. Idle speed stabilization is needed due to the effect engine load changes has on emission output, idle quality and vehicle driveability. The IAC system uses an ECM controlled idle air control valve (IACV) that regulates the volume of air bypassed around the closed throttle. The ECM controls the IACV by applying various input signals against an IAC program stored in memory.
There are four different types of IACVs used on Toyota models. These systems are referred to as:
• Duty-Control Rotary Solenoid
• Duty-Control Air Control Valve (ACV)
• On/Off Vacuum Switching Valve (VSV)
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