I have a 1998 Explorer with 213,000 miles on it. The check engine light only comes on when the weather gets cold. I had 2 of the oxygen sensors and mass air flow replaced about 2yrs ago. The engine light came on again with the same error codes P0171 and P0174. This only happens in the winter. I can warm it up and rev it up and it is fine. Put in drive and give it gas and light comes on. I just don't know why it happens in the winter and no other time of the year.

 

If you have the plastic intake manifold the cold weather contributes to some shrinkage and combined with some hardening of the intake manifold gaskets, causes some small intake manifold leaks..... Philip