99 f150, 5.4. 135,000 mi. Problem just started a couple of weeks ago but its gotten worse and made me late for work today. Never did get it started. Turn the key and she cranks just fine, but no start. Hold it to the floor and crank, it will start, but if you let off the throttle it will die. Will not catch idle. Doesnt even attempt to catch idle on the way back down. Any info greatly appreciated, I cant keep finding a ride to work.

 

Ok, so I went out and held the throttle to the floor to get it started. Once it started i held the throttle at about 1500 rpm's. Did this until it just started to get warm, let off the thottle and it dropped down to about 400 rpm (barely,barely running). I Jumped under the hood to check vacuum lines and whatever else i might see. Then i heard what sounded like pressure being released (pshoo) and it caught idle. Any Ideas?

 

get something long like a heavy screwdriver or even your lug wrench and give the IAC a couple of good whacks.
when it fouls it sticks and the truck won't idle.

if you whack it hard and then the truck idles, the iac is your problem.

on the 5.4 it is located on top of the motor directly under the passenger side windshield wiper post.

the only way to whack it is a jab in a spearlike motion.