Lincoln/Mercury Repair: check engine codes, vacuum leak, good mileage

Question
I have a 96 merc. marquis with yellow check engine light on.  I went autozone and got the codes.  they are P0174 and P0171, which means fuel system for bank one and two are too lean.  what does this mean and what should I do next?  the car is not getting as good mileage as should and it has a ping when accelerating hard.  Can I repair this myself very easily?

Answer
Hi Paul,

These codes would mean that you likely have a vacuum leak. If it was just one bank it might mean that you had a bad O2 sensor, but with both, it's a vacuum leak. Check your vacuum lines for cracks or missing. This would cause your poor milage and possibly the ping. The ping could be from bargain brand fuel as well.