RE: 1996 contour code 171 system too lean
timing chain rattle was a v6 contour problem on the 95 model...something about when the oil was allowed to settle after the car had been sitting awhile...would occur mostly on cold start and go away in a second or two...the fix was supposed to have taken place for the 96 model yr i believe
as far as the code goes, could be the o2 sensor or fuel injector???
99 expedition eddie bauer edition 93k