1997 Ranger check engine light on

the computer said is an emission problem and the gas millage is really low. someone mentioned that it might be the catalytic converter. Any toughts on this?

I forgot to mention, the light came on after getting the state inspection and oil change

What was code fom computer? My experience with bad gas milage along with poor performance was bad o2 sensors. Post code, that tells you where to start. Good Luck. Mine is 95 3.0

What was code fom computer? My experience with bad gas milage along with poor performance was bad o2 sensors. Post code, that tells you where to start. Good Luck. Mine is 95 3.0
the code is PO 171 and yes they told me is the o2 sensors. Are these difficult to install?

Not sure of your year on engine, so you may have 3-4 o2 sensors.$40-$50 each Easy to change with either special socket with groove down side for wire to go, or with open end wrench. As long as they aren't stuck like manifold bolts get. You might want to try cleaning your MAF ( mass airflow sensor) then disconnect battery for 10-15 min to clear codes. I've heard dirty MAF can throw po171 code also. Good Luck!!