My stock one did that when it was dying. I replaced it and it solved the problem. It should never get in the double digits, at least it never does on my car anyway. I'd say try a new O2 sensor either AC/DELCO or Denso NOT Bosch...

www.sparkplugs.com and coupon code "dodgetalk" (may not work anymore). My Denso O2 ran me $45 shipped to me w/ the coupon code....