I have a 2000 F-150 Ex Cab 4x4 with a 5.4 auto.

On cold mornings it will usually die once then start right up, but lately when it has been starting, the idle has been at 400 or 500 rpm, it usually idles around 1000 rpm. When it idles so low, it usually wont stay running if it is extremly cold, so i have to hold my foot in it until it warms up. Any thoughts or ideas as to what the problem might be? I am thinking maybe the IAC valce, PCV valve, or fuel pump.

 

My guess would be sticky IAC. Try giving it a tap when it is idling low an dsee if it wakes up. If that works remove it and clean it or replace it.

 

You hit the usual suspects. Startup fuel problems that go away after starting is that the fuel pressure has bled off overnight. When you first turn the key on the pump should run a second or two, then cut off until it sees RPM. Usually when we turn the key on we go right to crank and it doesn't have the second or two to build pressure. Try turning the key to run for 2 seconds, off, run for 2 seconds, then start. That would eliminate the most common startup fuel problem. If it did start right up after that, I'd live with it. Just do the little drill.

A stuck open PCV will over idle, a stuck closed or plugged line will under idle. In either case, the IAC should correct for it almost immediately.

If it is a consistent low idle after starting, yes, it sounds like the IAC is stuck. When it's warm, the position the IAC is stuck in is likely enough so you don't notice it except on startup. You're luckly it stuck in a good position for warm running. You can still test this. If you turn your air conditioner on (or the defrost) while idling the idle should dip for 1/2 second or so and then pick right back up as the IAC corrects the idle speed. When you turn off the A/C it should flare for 1/2 or so and settle right back down. If the A/C lowers the idle after warm and it comes back after you turn it off, the IAC is stuck. I'd replace it, simple and on most cars around $70 for the part.