I have a 99 F250 with the 5.4 w/Automatic...

Sometimes,  when I start it when the engine is cold,  it'll fire up, idle
just for a second or two and then want to die. If I stay on the gas as soon
as it starts, I can keep it running.  All of a sudden, as I'm keeping it
running, it seems like something kicks in and the idles way up like it
should when running normal.  I can then let off the gas and it will idle
fine.  I usually have to keep on the gas until it reaches normal operating
temp and sometimes a bit longer.  No engine lights come on or anything, it
just does that.  It wont' do it all the time, just sometimes.

It "seems" that when its really humid outside, like right after a rain, or
in this miserable heat and humidity right now, it does it more often.
Almost never when its dry outside, it "seems" anyway.  It's done this since
it was new, and I've had it to the dealership about this trouble, but they
have no idea, since its warmed up when I get there and even if it sat
overnight, there's no guarantee it would do it the next morning either.

Any ideas guys and gals?

TIA,

Doug