changed upsteam o2'sno different do i need to do downstreams?
No. Unless something is wrong with them.
why did you change o2 sensors?
check engine light and codes po 171 ,174 with brand new engine about 3000 miles ago
You most likely have a vacuum leak causing the lean codes.
Yeah, lean codes on both banks is very likely a vacuum leak.
Looking for a Used Windstar in your area?
CarGurus has 687 nationwide Windstar listings and the tools to find you a great deal.
Search Ford Windstar Questions
Ford Windstar Experts
Related Models For Sale