truck turns over wont run no sounds or leaks unsual perfect turn over every tim?

What is your question?

I was driving home left the navi running ran into the house and silently with no sputter no warning signs of any trouble it stalled. No lose of power no issues driving at all nothing said to me hey maybe navi should be looked not one concerning sign at all it just stalled quietly when I got in to turn it over it did perfectly but then would not actually run and it is still this exact way after replacing starter wiring and tune up and checked everything I can think of. it is like starting a vehicle with a key that belongs to the style but not the particular vehicle it turns over but wont actually start it has been six month and still turns over every time but wont stay running. I have had a few people say a security feature and I have to reset, others a computer and key issue but why would the key work then not in one moment? this is been six month there is not much more I can fix i feel if it was the injector i would have seen some signs of sputtering or something. help !

What makes this problem better or worse?

It is the same perfect turn over every time

How long has your 1999 Lincoln Navigator had this problem?

6 months cant figure out what is causing it