o2 Sensor Replacement?

[sofdee]

My son has a 98 Lincoln Mark VIII in Florida and his check engine light came on, so had it diagnosed and they told him it was a code 171 and 174, which I guess means replace the o2 sensors? Is it possible for him to do this easily himself or is it better to have a mechanic do this? We're also researching the best deals for the parts (he's very tight on money right now), so is it ok to use Borg Warner parts rather than Bosch? thanks in advance

 

[98LSC32V]

Have an exhaust shop do it. The 98 has 4 oxygen sensors but the front 2 are the only ones that matter. I would get Motorcraft O2 sensors I have heard bad stories about Bosch.

 

[fossten]

Have an exhaust shop do it. The 98 has 4 oxygen sensors but the front 2 are the only ones that matter. I would get Motorcraft O2 sensors I have heard bad stories about Bosch.

I've got a 93 that needs O2 sensor replaced too. Do I need two of them or what? How do I change it?

 

[jdlmkviii]

Order from Max at FiveStar. He carries the Motorcraft OEM replacement and offers discounts. I got them for $57 a piece (2) and I just had a shop put them in. Cleared check engine light, smoothed the idle, and got rid of a little sputtering problem.... also performs a little better too.

 

[fossten]

Order from Max at FiveStar. He carries the Motorcraft OEM replacement and offers discounts. I got them for $57 a piece (2) and I just had a shop put them in. Cleared check engine light, smoothed the idle, and got rid of a little sputtering problem.... also performs a little better too.

how much labor did they charge you?

 

[formerknown]

Just replace the front set, where the O2's are in the exhaust manifold. The one's after the cats are useless and throw codes. Just delete them with MIL eliminators and sleep better at night. Plus, you can be worry-free if your state does OBDII tests like mine. The MIL eliminators fool the computer and you'll pass every time. Time for longtubes...:gr_devil:

 

[jdlmkviii]

how much labor did they charge you?

Sorry I really don't know, I had them do a bunch of other stuff too. Couldn't be more than $50 or so.

 

[dertyclown]

bad stories about Bosch.

they are sh!t trust me and they don't like to give you your money back eather.
put the OE parts in your self it might take an hour if your using the little car jack.

 

[fossten]

bad stories about Bosch.

they are sh!t trust me and they don't like to give you your money back eather.
put the OE parts in your self it might take an hour if your using the little car jack.

Anybody know where I can get instructions?

 

[rmac694203]

I don't know anything about changing them except I'm pretty sure someone on here said once before that they are kind of a pain in the ass to get to. Not 100% on that though.

 

[2001LS8Sport]

Have an exhaust shop do it. The 98 has 4 oxygen sensors but the front 2 are the only ones that matter. I would get Motorcraft O2 sensors I have heard bad stories about Bosch.

That is not quite true. The rears are used to compare against the fronts to see if the cats are operating properly. They are there for a reason.

I'm not sure what those codes are, but you need to make sure why it is setting the code. Just reading a code and thinking the O2 sensors are bad is not your best approach. Unless the sensor is so bad that it is stuck rich or lean, you may need to check elsewhere. Sometimes you get codes that indicate the sensor is having problems when in fact it is something else in the engine that is causing the problem and the sensor is operating correctly...but reading way out of specs due to the other problem. The best test I know for an O2 sensor is to check the cross counts. These should be fast and consistent. If they are slow, that indicates the engine is operating correctly but the sensor is becoming weak and needs replacement. I would suggest you do a little more diagnosis on the car before you arbitrarily just throw parts at it. All that being said, sensors do wear out and if it has over 50,000 miles on it, it might be time to freshen them anyway.

Changing them is very straight forward. Disconnect the wire harness and use the box side of a wrench by running the wire through the wrench first. If they have been on the car for a long time, they may be very difficult to get loose. In that case, use a little heat around the bung and they will come out. Just remember to do yourself and the next guy a huge favor and use some antisieze on the sensor when you install the new one. Also...DON'T TOUCH THE SENSOR END WHEN HANDLING IT OR GET ANTISEIZE ON IT!!

 

[jdlmkviii]

Anybody know where I can get instructions?

Probably can't be all that tough. If you get the car up off the ground, look up between the 1st and 2nd cats and the manifolds. Right after the cats you'll see these little Pen lookings objects that are about 2-3 inches long sticking perpendicular out of the pipe. You'll also notice a wire comes out of the back and has a little clip up the wire a little bit. All you need to do is unclip the old wires, and screw the old O2's out using a socket wrench (don't know what size). And reverse the steps for putting the new ones in. Only problem with this job is you'll have a lot of trouble getting your hands up there, most people just say F-it and have a shop do it because in most cases you have to drop the exhaust. Good luck to you though.

 

[2001LS8Sport]

you can't use a socket wrench unless you either use an O2 sensor specific socket or cut the wires off first.

 

[fossten]

That is not quite true. The rears are used to compare against the fronts to see if the cats are operating properly. They are there for a reason.

I'm not sure what those codes are, but you need to make sure why it is setting the code. Just reading a code and thinking the O2 sensors are bad is not your best approach. Unless the sensor is so bad that it is stuck rich or lean, you may need to check elsewhere. Sometimes you get codes that indicate the sensor is having problems when in fact it is something else in the engine that is causing the problem and the sensor is operating correctly...but reading way out of specs due to the other problem. The best test I know for an O2 sensor is to check the cross counts. These should be fast and consistent. If they are slow, that indicates the engine is operating correctly but the sensor is becoming weak and needs replacement. I would suggest you do a little more diagnosis on the car before you arbitrarily just throw parts at it. All that being said, sensors do wear out and if it has over 50,000 miles on it, it might be time to freshen them anyway.

Changing them is very straight forward. Disconnect the wire harness and use the box side of a wrench by running the wire through the wrench first. If they have been on the car for a long time, they may be very difficult to get loose. In that case, use a little heat around the bung and they will come out. Just remember to do yourself and the next guy a huge favor and use some antisieze on the sensor when you install the new one. Also...DON'T TOUCH THE SENSOR END WHEN HANDLING IT OR GET ANTISEIZE ON IT!!

See, I've already taken it to two mechanics, that's the problem. One gave me a tuneup, which only improved the idle problem I was having, the other said it was my torque converter. Neither mechanic fixed the problem. I finally took it to the Zone to get the codes pulled. I don't think the computer is just gonna say, "Hey, you need to fix your O2 sensor!" I don't have any other choice but to throw parts at it. I am sick of paying for diagnostic checks at $60.00 a pop with no results.

I don't understand what you mean by cross counts. I'm not a mechanic, or I probably would have fixed this already without asking for help.

I don't have a clue what you're talking about as far as how to change the sensors, so I'll probably have to pay someone to do it.

 

[2001LS8Sport]

If you're unsure about how to change the sensors, you are probably better off having someone do them for you. May be cheaper in the long run too. But they really aren't that hard to do...other than the wire, it's not any more difficult than changing a spark plug. As a matter of fact, it uses the same size thread and pitch that the old style spark plugs used!!

Ok, cross counts are what an 02 sensor does when measuring the oxygen content in your exhaust. Many people believe that the sensor gives you a steady reading of the oxygen content it measures. That's not how it works. It constantly goes from rich to lean. At it goes rich, the ECM leans the mixture, then when it goes lean, it richens it back up. It does this VERY quickly! The number of times it goes from rich to lean is what's called cross counts. As an 02 sensor gets old and worn, it can't adjust as quickly and the number of cross counts slow down. You need to remember that the 02 sensor does not use vehicle power to measure 02 content. It generates it's own power...and it's an extremely small voltage. Somewhere between .1 and .9 volts. (that's why it's NEVER smart to tap into an 02 sensor for any type of aftermarket guage or AF meter...install it's own sensor) Now, just about all sensors these days have 3 or 4 wires going to them and DO have power to the sensor. However, that is only for heating the sensor. It needs to be hot to operate and the car cannot go into closed loop (that's where the ECM is in total control of the air/fuel ratio) until the sensor is up to temp. In the old days, the manufacturers let the exhaust heat the sensor. But that left it in open loop for too long. Now they heat the sensor to get it into closed loop as fast as possible so the ECM can control things and meet emissions. Until it's in closed loop, it's running on a preset MAP in the computer that uses other sensors...but not the 02 sensor.

Hope this helps.

 

[fossten]

If you're unsure about how to change the sensors, you are probably better off having someone do them for you. May be cheaper in the long run too. But they really aren't that hard to do...other than the wire, it's not any more difficult than changing a spark plug. As a matter of fact, it uses the same size thread and pitch that the old style spark plugs used!!

Ok, cross counts are what an 02 sensor does when measuring the oxygen content in your exhaust. Many people believe that the sensor gives you a steady reading of the oxygen content it measures. That's not how it works. It constantly goes from rich to lean. At it goes rich, the ECM leans the mixture, then when it goes lean, it richens it back up. It does this VERY quickly! The number of times it goes from rich to lean is what's called cross counts. As an 02 sensor gets old and worn, it can't adjust as quickly and the number of cross counts slow down. You need to remember that the 02 sensor does not use vehicle power to measure 02 content. It generates it's own power...and it's an extremely small voltage. Somewhere between .1 and .9 volts. (that's why it's NEVER smart to tap into an 02 sensor for any type of aftermarket guage or AF meter...install it's own sensor) Now, just about all sensors these days have 3 or 4 wires going to them and DO have power to the sensor. However, that is only for heating the sensor. It needs to be hot to operate and the car cannot go into closed loop (that's where the ECM is in total control of the air/fuel ratio) until the sensor is up to temp. In the old days, the manufacturers let the exhaust heat the sensor. But that left it in open loop for too long. Now they heat the sensor to get it into closed loop as fast as possible so the ECM can control things and meet emissions. Until it's in closed loop, it's running on a preset MAP in the computer that uses other sensors...but not the 02 sensor.

Hope this helps.

Nice. Good info. Thanks. I'll put it in the shop next week. Shouldn't cost too much labor.

 

[Frat-man-du]

See, I've already taken it to two mechanics, that's the problem. One gave me a tuneup, which only improved the idle problem I was having, the other said it was my torque converter. Neither mechanic fixed the problem. I finally took it to the Zone to get the codes pulled. I don't think the computer is just gonna say, "Hey, you need to fix your O2 sensor!" I don't have any other choice but to throw parts at it. I am sick of paying for diagnostic checks at $60.00 a pop with no results.

I don't understand what you mean by cross counts. I'm not a mechanic, or I probably would have fixed this already without asking for help.

I don't have a clue what you're talking about as far as how to change the sensors, so I'll probably have to pay someone to do it.

You are right codes only tell you what kind of test to run, the test(s) then detemines the next step(s) until you get to the root cause of the code. You can often replace parts all day long and still have the issue. Replacing O2 sensors is not a big deal and is good PM anyway. I replace mine every 75K just for PM and also gets me a tad better gas milage.