I have a 2000 Mountaineer 5.0 that has started having idiling problems mainly with cold crank. It will idle around 400 instead of the normal 1200. when the idle does manage to come up i can hear it start to suck air like it should. Im wondering if it could be the idle control sensor or the mass air flow. Any info you could give would be greatly appreciated

 

When the engine warms up, does it idle fine? Please let us know, this can be important in figuring out what's wrong.

 

This sounds like a classic IAC problem. The IAC (Idle Air Control; Ford is SO proud of their acrynoyms) is what controls the idle. It is usually extremely trouble free, until they get dirty. This sound like the case.
You could start by scanning for codes (which would be a P0505 or P0506, along with a bunch of other historical codes, which this powetrain was fond of setting), but since we already know that the truck starts and runs at 400 rpm (which, incidentally is the EXACT speed these will run with the IAC unplugged), if you would have someone start the car, then whack the IAC with a screwdriver handle (use a heavier one, just don't beat the thing silly), the said truck will probably start to idle perfectly and most likely run fine the rest of the day.
But there's more. This IAC is stated as being 'non-cleanable'. This has never stopped me from spritzing the throttle body with carb cleaner, concentrating specifically on the air intake to the IAC (which is before the throttle plate, and on top, if memory serves correctly) and this will usually help them for a while. How long is a mystery, because every car is different, and I don't have my Crystal Ball back from the Wizard to make such predictions. It may last a day or a year.
Or, if you're in a sporting mood, you might just install a new one. Also, a caveat here. IF you elect to clean the throttle body, which is recommended with a cloth rag and nothing else, you can try with carb cleaner, but this tends to erode the teflon plating on the butterfly, and they can stick when you depress the throttle, which can be irritating. This usually occurs much more often when an aftermarket air filtration system (K&N comes to mind) is employed. You'll have to make the judgement.
These also benifitted from a good old fashoined tune-up also, paying particular attention to the plug wire routing. These were really good for misfires that would destoy the catalysts.
Just food for thought. Otherwise, they were a very durable powetrain.
Good luck!

 

cougar_fan, it only has problems on a cold start, and not every time. Usually after about 30 seconds the engine will come up to its correct idle. I will check the IAC greasemark, and let ya'll know what i find. Thank You.