p0171 andpo174 mean that you're car is running lean
Trouble code P0171 means: Fuel Trim System Lean (Bank 1) Trouble code P0174 means: Fuel Trim System Lean (Bank 2)
Trouble code P0171 means: Fuel Trim System Lean (Bank 1) Trouble code P0174 means: Fuel Trim System Lean (Bank 2)
Trouble code P0171 means: Fuel System Too Lean (Cylinder Bank 1) Trouble code P0174 means: Fuel System Too Lean (Cylinder Bank 2)
It means your vehicle is running lean you will need to replace the intake manifold gasket, as it is plastic and the seal wears out.
Trouble code P0171 means: Fuel System Too Lean (Cylinder Bank 1) Trouble code P0174 means: Fuel System Too Lean (Cylinder Bank 2) These 2 codes are common indicators of a well-known failure on the 1999-2003 Windstars. Be sure to review the additional information in the "Related Questions" below...
Trouble code P0171 means: Fuel Trim System Lean (Bank 1) Trouble code P0174 means: Fuel Trim System Lean (Bank 2)
P0171-system too lean bank 1 and P0174-system too lean bank 2
Trouble code P0174 means: Fuel System Too Lean (Cylinder Bank 2) Trouble code P0171 means: Fuel System Too Lean (Cylinder Bank 1)
lean bank 1 lean bank 2 fuel trim limits reached
P0171, system too lean (bank 1). P0174, system too lean (bank 2). Start with checking for a vacuum leak.
Lean condition detected on banks 1 & 2 (left and right sides). Most commonly a dirty mass air flow sensor, or possible vacuum leak.
Read through the "Related Question" that discusses a common problem with the Windstars and rough idle - check engine codes P0171 & P0174. That might be part of your problem too...