P0171 Ford -97 Aerostar bank one running lean.

Question

97 Ford Aerostar po171 bank one running lean getting bad gas mileage .

Answer 1

P0171 Fuel trim lean Bank 1

Vacuum leaks are the main cause for a lean fuel trim. There is a lot to look at when it comes to a lean condition. The PCV hose tends to rupture or collapse causing a lean condition. the vacuum connection tends to slip off, When the engine is lean the RPM is shifted higher. Look for vacuum leak, you may just be able to here it

 Here is a connection that just would not stay put .  Connection like these tend to disconnect and some plastic lines tend to break look for vacuum leaks