99 Merc Mountaineer keeps idiling out! HELP!

[SarahGuess]

I have a 1999 Mercury Mountaineer. My truck keeps idiling out. I will crank it and immediately it will idle out. I will hold the gas down for a few minutes and it will get into gear and idle out again. This will continue for about 10 minutes. When I finally am able to go it will jump sort of, and then go. It will still feel like it will cut off, until about 5 minutes of straight driving then it will go back to normal.
I have had the wires, plugs, filter, and oil changed, and that seemed to have fixed the problem for about a week. Then it started doing it again. So I replaced the altenator and again that seemed to have fixed the problem for about a week. Then it started again. Lastly and recently I replaced the Massive Air Flow Sensor. That seemed to have fixed the problem for about a week and a half, and then it started the same problem all over again. I have hooked it up to a computer scanner and the code P1507 was coming up. I called Autozone and that code lead into about 4 different problems. Could anyone please offer advice of what to look for or what could be causing the problem.
Please Help!!!!

[shorod]

The code P1507 for your Mountaineer indicates an Idle Air Control (IAC) underspeed error. According to the factory service manual, this code indicates that the PCM detected an engine idle speed that is less than the desired RPM. Also per the service manual, possible causes are:

• IAC circuit open
• IAC circuit short to PWR
• VPWR to IAC solenoid is open
• Air inlet is plugged
• Damaged IAC solenoid
• Damaged PCM.

A good test to see if the IAC is doing what it's supposed to would be to unplug it and see if that changes the way the engine starts and runs. Also, once the engine is running decent, turn the A/C on (if it's charged and works) and see if the engine speed drops significantly and stays low.

-Rod