What does it mean when I have one big puff of smoke come out of the exhaust upon starting my 2005 f150?

 

This usually means you are burning oil. Sometime the valve-stim seals leak oil into the heads and it smokes while the engine is cold. When the engine warms up, the seals swell and the oil doesn't seep in as much. While the engine is sitting up the oil builds up. This should not be the case with a truck as new as yours unless it has been driven excessively hard, or overeheated, but it is a possibility. Other than that, it could be a sensor, causing a bad gas/air mixture. This, however, should show up in the computer codes. Get Autozone or someone to run a scan for codes, and see if any show up. Good Luck!!
W.O.W.

 

I have a 2002 F150 Lariat with the 5.4 and has just recently started doing the same thing, i only have 62,000 on it so i was disappointed. I was also told it was probably the valves leaking.