Idle Speed

When there is a problem with the idle refer to Idle Air Control (IAC) System Diagnosis.
^ System too lean (High air/fuel ratio) - Idle speed may be too high or too low. Engine speed may vary up and down, disconnecting the IAC valve has no effect.
^ System too rich (Low air/fuel ratio) - Idle speed too low. Scan counts usually above 80. System obviously rich and may exhibit black exhaust smoke. scan tool and/or voltmeter will read a Heated Oxygen Sensor (HO2S) signal fixed above 800 mV (0.8 volt).