How do you replace an O2 sensor on your 1999 Ford Contour?

Answer 1

very easy its best to have the socket for an o2 sensor it has a slit down the side to allow for the wire to come out the side available at any auto parts store then you will find it in the front of the engine right behind the radiator it will have 4 wires coming out of it all you do is follow the wires to the wiring harness the detach the clip. then you use the socket to lossen it then unscrew the rest of the way out at this point wheather you bought one with the clip on it that attaches to the factory harness or if it has bare ends on the wires you may need to splice the wires to the original clip then screw it in place and your done 30 minutes tops

If you are talking about the 2.5 V6, then it's not as easy. According to several sources I've looked at while venturing to do this myself, there is debate among the experts, including Ford, Mercury, Autozone, Pep-Boys, Bosh website, Autoparts website and the toothless mechanic standing next to me in the Autozone checkout lane.

I think there are 4. I have found, and replaced 3 of the 4, and the fourth one, or AKA Bank-1 Upstream HO2, is between the firewall and the engine. The guys at the Mercury parts desk say that it's not really an O2, rather a catalytic sensor (Whiskey Tango Foxtrot).

Advice - Get Autozone to run a free diagnostic and tell you exactly which one it is, and replace only that one. I allowed my daughter to manage this thus I got the "Daddy, they're all bad" answer. Of course, being a good pop, I set my brain aside, believed what she said, spent $150 more than I had to, and found a different problem. You might be thinking about now, why would I listen to this person who got suckered by a teen-ager. Well, I'm just sharing something that will maybe help. I don't recommend the Hayne's manual either - it's pretty confusing. The Autozone freebie, so far, is better.

Semper Gumby

Oh - me again, the DA. The funky wrench the previous guy mentioned is a waste on the V6. Just use a (7/8) wrench. However, I may later learn that the funky wrench is the only way to get to the mystery O2. If so, I'll eat crow.

This is specific to the 1995 v6 model (and any other model years that may be identical to it as far as O2 sensors are concerned). The front bank sensor is relatively easy to do with a normal wrench. The rear is another matter as you can only access it from above. At the very least, you will have to remove the rear bank spark plug wires (better ID them with masking tape?) and the ignition coil (not hard). There is a metal track that provides support to a loom of wiring which traverses the engine from side to side, attached to the rear of the engine and close to the fire-wall. Only two small nuts hold that on, but you will have to use some force to remove the mounting tangs of this track off of the studs it is attached to. I was offered the loan of a modifed wrench for the sensor so I used it (the proper socket may have been a better option if you're willing to make the investment, but I don't hope to ever be able to make the comparison). As for the wrench, get a cheap 7/8 combination wrench and cut it down to no more than what you need to fit your hand, keeping in mind you are going to need the box-end of it. Grind over the cut off end to eliminate any sharp edges. Locate the sensor by hand (your eyes won't help here) and follow the wire up to the connector. Disconnect the sensor and hang on to the wire, placing the box end of your wrench over the wire. Follow it down onto the sensor and get the wrench over the sensor nut in such a way that you are going to be able to loosen it. If memory serves, you'll be pushing down to loosen. Once you have cracked it loose and maybe went through a couple more wrench-arcs, it should turn out by hand. Expect to spend about an hour replacing the back one. You might be tempted to do only the front if an engine fault code indicates the problem is the front one, but these are considered normal maintenance items, and you will be doing the rear at some point if you keep the car. .