it start to pull like 2 times, like if it was running out of gas or something.It does not happen all the time.l gave it all the required maintenance.What is wrong with it?

Did you change the gas filter?? also the fuel injectors may need cleaning out and have the codes read you might have a coil going bad, hope this helps.

The 2003 Navigators were the worst Navigators built. This is coming from me (a huge Ford guy): my dad had a white 03 & it was the most unreliable vehicle we have had. Every 20,000 miles there was an electrical problem with the power third row seats, some annoying & loud clicking noise coming from the back, & a lot of side view mirror problems. The battery also died after 60,000 miles & a valve was not functioning right & had to bring it into that.

For some reason though, the 2004's-2007 is r really reliable according to consumer reports. We should have waited a year or two when buying.

Not sure what it is l do not think pulling is the right term to use maybe its hesitating or surging or missing but what ever it is it should not be doing it. You got a sensor somewhere malfunctioning could even be a sensor for speed or transmission. sounds like a trip to the dealer.