02 grand Cherokee running rich

Me and a friend of mine just put a complete
defferent motor in my jeep mine had a rod
knocking so we got a used motor from a junk yard
that the motor was in a wreck jeep and we
installed it in my jeep now it runs rich and hard to
start we put in New sensors and sent it to the
dealer to have them fix it they say that every thing
is good and it still runs rich and hard to start we
need someone else opinion on what could be
wrong with my jeep we are both losing are sleep
and minds on what could be wrong with my jeep it
has a 4.7 motor in it