I am working on a 2003 Santa Fe 2.4L - Idled a little rough without A/C and very bad with A/C on. It also threw up a P0506 low idle speed code. I cleaned the throttle body and mass air flow sensor and the idle without A/C smoothed out and the low idle speed code did not return. But the Vehicle still has a very rough idle, to the point of dying with the A/C on. When you kick on the air, the rpms drop as would be expected in any vehicle, but the system isn't adjusting the idle up to compensate like most vehicles. Any ideas would be appreciated.

 

I am thinking IAC valve...does anyone know how to test it?

 

Cleaning idle air control valve solved the problem. Thought I would share despite the fact that no one commented. Hopefully this will help someone in the future. IAC Valve is located directly under the throttle body, inside of it a small plate slides open and closed to allow more or less air. It had frozen in place and spraying it with carb cleaner and manually moving it broke it loose. You can check the valve unbolting it from the car but keeping it plugged in. turn the key to on (do not start) valve should activate and the plate should move inside the chamber...if it doesn't move you probably need to clean or replace the valve.