The idle air control valve, or IACV, in the Nissan Maxima is responsible for regulating the amount of air that flows through the throttle body to maintain a constant idle speed. Maxima's powertrain control module controls the IACV electronically. Problems with the IACV will cause your car not to idle properly or even to stall out. The Maxima should idle at a speed of approximately 1,000 RPM when it is not in gear and 800 RPM when it is in gear.
If your Maxima's engine has developed an air leak somewhere in the manifold or throttle body, the computer may close off the airflow that is coming through the IACV in an attempt to hold in air and maintain the proper idle. Too much air will cause the vehicle to idle too fast, increasing the engine's RPM reading at an idle. This will result in the idle air bypass solenoid extending all the way out and restricting the airflow through the valve entirely, rendering the valve completely ineffective for maintaining proper idle speed.
The idle air control solenoid can experience a short within the wiring or circuits that will cause your Maxima's check engine light to come on and cause the vehicle's computer to generate error codes. This may cause the IACV to stop working and the vehicle may idle poorly or even stall out when it is supposed to be idling.
Vacuum leaks will affect the amount of airflow your Maxima's idle air control valve is receiving and can cause the vehicle to idle both too high and too low. Vacuum leaks are not actually a problem with the idle air control sensor itself, but with the connections to and from the control sensor through the throttle body and intake. Vacuum leaks are a common cause of idling problems, which are then typically blamed on a faulty IACV. It is important to check your Maxima for vacuum leaks before replacing the IACV on your motor.
