I had the same problem and the local Ford dealer replaced 3 oxygen sensors (and they're expensive!). Then, I replaced the fuel filter (which is inconveniently located under the car, in front of the tank.) Nothing ever seemed to work. Then a neighbor explained that oxygen sensors go off when there isn't enough oxygen, not because they're broken!!! Everyone want to blame the sensor...including the bloody dealership! He had three Tauruses, each with more than 150,000 miles. He lifted my hood, reached under the battery and retrieved a piece of vacume hose which was cracked and worn. $2.00 later, the car has been running great for the last two years. Check all your vacume hoses (and there's a bunch of them!) and replace the stuff that's worn and cracked. If you replace every vacume hose in the car, you won't have $20 invested in hoses and you'll likely fix the problem.