Idle Speed Control Valve

Idle speed is kept constant by an idle speed control valve, which supplies engine with necessary amount of air. Idle speed control takes place during period in which throttle potentiometer, or TPS, detects idle setting. The pre-programmed idle speed values in PCM are compared with actual operating values and corrected to compensate for component wear and other factors, such as minor air (vacuum) leaks.

When engine management system detects engagement of a drive range (1, 2, 3 or "D"), idle speed is increased by idle speed control valve to compensate for engine speed drop caused by engagement of torque converter. On A/C-equipped models, idle speed is also temporarily increased when A/C system is switched on. Upon receiving A/C compressor signal, quantity of air required for idle speed is corrected.