Idle Speed/Throttle Actuator - Electronic: Description and Operation
DESCRIPTION AND OPERATION
The idle speed of the engine is controlled by the idle air control valve.
The valve changes the amount of air bypassing into the intake manifold in response to electric current controlled by the engine control module. When the idle air control valve is activated, the valve opens to maintain the proper idle speed.
1. After the engine starts, the idle air control valve opens for a certain time. The amount of air is increased to raise the idle speed about 150 - 300 rpm.
2. When the coolant temperature is low, the idle air control valve is opened to obtain the proper fast idle speed. The amount of bypassed air is thus controlled in relation to the engine coolant temperature.
1. When the idle speed is out of specification and the scan tool does not indicate diagnostic trouble code P0505 or P1508, check the following items:
^ Adjust the idle speed
^ Air conditioning signal
^ Alternator FR signal
^ Automatic transaxle gear position signal
^ Brake switch signal
^ Starter switch signal
^ PSP switch signal
^ Fast idle thermo valve
^ Hoses and connections
^ Idle air control valve and its mounting 0-rings
2. If the above items are normal, substitute a known-good Idle air control valve and readjust the idle speed.
^ If the idle speed still cannot be adjusted to specification (and the scan tool does not indicate diagnostic trouble code P0505 or P1508) after idle air control valve replacement, substitute a known-good engine control module and recheck. If symptom goes away, replace the original engine control module.