Mitsubishi Repair: Idle air control malfunction (P0505), throttle position sensor, intake manifold gasket

Question
I have a 1998 mitsubishi mirage DE and my car idles up when I have my foot on the break and im using Air conditioning. It feels as if the car is going to turn off. I got it diagnosed and autozone said their was an idle air control malfunction and needs a new idle air control. I went to the junk yard and got the part then had it installed, but the problem was only fixed for one day.  What are other solutions to fixing this problem?

Answer
Michael,
Is your check engine coming on again with that same code?  If so, that junkyard IAC you installed may again be failing.  The IAC is a very sensitive part, and ones from junkyards may be just as bad.  Though other things that can cause poor idle or idle surge are the throttle body, throttle position sensor, EGR valve, or even a leak in the intake manifold gasket.  You can check those items.
Good luck!