Fast Idle Air Valve
The function of the FIAV is to increase the idle speed anywhere from 801RPM to 1500RPM when the engine is cold. It does this by using coolant from the engine to heat a wax ball that is attached to a valve. When the coolant is cold the valve is open allowing air to bypass the throttle body which increases the idle RPM anywhere from 801RPM to approximately 1500RPM. When the coolant warms up the wax the valve is closed and the idle returns to its normal speed.
The most important thing to know about your fast idle air valve is that if you clean your throttle body with carb cleaner you can ruin your FIAV!
1500RPM Is the MAXIMUM cold idle speed attained at -4 degrees F. After the car has been allowed to fully cool the engine coolant temperature becomes that of the outside ambient air temperature (+or- 1 or 2 degrees F) which means cold idle RPM will vary in a range of 801RPM to 1500RPM. The charts below will help you better figure what your cold idle speed should be on initial engine startup using a given outside temperature to approximate initial cold idle RPM.
Go to Jeff Lucius's webpage to see pictures and for more detailed information: http://www.stealth316.com/2-3s-tb.htm
Go here to reference basic idle speed adjustment procedure: http://www.3si.org/wiki/index.php/Idle_Speed_Adjustment