The worst damage you can do to your vehi is well running rich, which in turn is bad gas mileage which in the long run will cost you more than $300.00 in a years time unless you only drive 5 miles a day. Second is that burning rich and in a closed loop cycle you could cause a meltdown in your converter which in turn will clog up and cause very poor performance and baaaad gas mileage, so there you have it faqs on running with a bad O 2 sensor. Try to find a used one it may give you a few thousand miles before it goes bad too. Good luck with your adventure.