2003 Ford Focus • 65,000 miles

I have a P0302 DTC and I have a P2274 oxygen sensor stuck too lean. How do I go about testing the oxygen sensor, and what would cause this sensor too be stuck too lean.I have posted this problem before but I am just getting around too trying to take care of problem, and like I said before it does not misfire all the time but when I turn on ac and put a load on it it will misfire all the time turn it off and it might not misfire right away it will run for awhile without misfiring, then sometimes it will start then it will go away, but it always misfires when ac is on. Why is the oxygen sensor stuck too lean unburned fuel and is it stuck lean because of misfire, it will only misfire at idle does not stall or die just at idle
Randy sharp
August 19, 2013.

Check your fuel pressure with a gauge it may be to low causing both problems then check for a vacuum leak at that cylinder

Aug 19, 2013.