1. Open the hood of your Nissan Quest 2004.
2. Locate the throttle body. It is usually a cylindrical-shaped component connected to the intake manifold.
3. Look for the IAC valve on the throttle body. It is often attached to the side or bottom of the throttle body.
4. The IAC valve may have an electrical connector attached to it.
Please note that the exact location and appearance of the IAC valve can vary depending on the specific engine and model year of your Nissan Quest. If you have difficulty finding the IAC valve, it's recommended to consult your vehicle's service manual or seek assistance from a qualified mechanic.