Idle Speed Control (ISC)
The Idle Speed Control (ISC) system increases engine idle speed when A/C compressor is operated, without changing throttle valve position. The system consists of a solenoid valve, air by-pass valve and air by-pass passages in the fuel injection mixer. See Fig 1 .
The ECU energizes the solenoid valve when A/C compressor switch is closed. When energized, the solenoid valve allows the air by-pass valve to open. When by-pass valve opens, additional air is admitted below throttle valve to increase idle speed. This system helps prevent engine stalls due to engine load changes.