Change o2 sensor?

[garlicbreadman]

Hello,

My friend bought a 96 integra recently with 200k miles. I think it has the original o2 sensor and could be the cause of below average gas mileage(20mpg). No check engine light.

Do o2 sensors fail slowly or right away? If failing slowly, does gas mileage also go down slowly?

An aftermarket o2 sensor on this car is only about $35,(NGK/NTK brand) so i am thinking about just changing it out.

 

[slacktide_bitog]

NGK/NTK and Denso both make great oxygen sensors. If it's easy and cheap to do so, why not?

 

[Noey]

The O2 sensor sits fore of the cat, so all the emissions that the cat would normally burn off can easily clog it, usually they're replaced at either the 30k or 60k service. Typical symptoms include rough or uneven idle, poor acceleration, reduced MPG. If you don't know if it's been replaced, it's a good idea to replace it, with OEM.

 

[zrxkawboy]

Originally Posted By: garlicbreadman
If failing slowly, does gas mileage also go down slowly?



Yes!

 

[Quest]

Originally Posted By: Noey
The O2 sensor sits fore of the cat, so all the emissions that the cat would normally burn off can easily clog it, usually they're replaced at either the 30k or 60k service. Typical symptoms include rough or uneven idle, poor acceleration, reduced MPG. If you don't know if it's been replaced, it's a good idea to replace it, with OEM.


Replaced every 30~60k? Never heard of that.

also: emissions that normally burn off can easily clog it?! Where do you get that idea from?!?

Q.

 

[tomcat27]

"replaced every 30 or 60k"? no. can it cause a drop in mpg? certainly - but so can a lot of other things; including a thermostat. is it a good idea to change after 200k miles? absolutely! the best way to diagnose is with an OBD reader that allows you to watch the data stream - then you can see the output of the O2 sensor. a 96 should be an OBD2 system, with 2 sensors per cat; normally 2 per cylinder bank. I highly recommend OEM; although NTK is OEM for some manufacturers.

 

[eljefino]

Old o2 sensors can get fouled with soot, dry or oily. This makes them respond slower and the fuel mix can get more out of whack before they "swing back".

I 2nd the thermostat idea.

 

[PandaBear]

I usually change mine when the smog check result is near failure at low speed (we put cars on dyno for smog in CA). They are easy to replace so at 200k I'd just replace it anyways.

I've used both Denso and NTK on my 97 Integra before, they both work great.

 

[Trav]

Originally Posted By: Quest
Originally Posted By: Noey
The O2 sensor sits fore of the cat, so all the emissions that the cat would normally burn off can easily clog it, usually they're replaced at either the 30k or 60k service. Typical symptoms include rough or uneven idle, poor acceleration, reduced MPG. If you don't know if it's been replaced, it's a good idea to replace it, with OEM.


Replaced every 30~60k? Never heard of that.

also: emissions that normally burn off can easily clog it?! Where do you get that idea from?!?

Q.


Back in the early 80's VW/Audi had a O2 sensor flag that came on every 30K and was a bugger to shut off on some models.
You were supposed to change the O2 but i don't know anyone that ever did. thats where this comes from, its outdated.

 

[Quest]

Originally Posted By: Trav

Back in the early 80's VW/Audi had a O2 sensor flag that came on every 30K and was a bugger to shut off on some models.
You were supposed to change the O2 but i don't know anyone that ever did. thats where this comes from, its outdated.



Those were the good times, I'd say.

Now, I don't see O2 sensor (esp. upstream wideband O2 sensor) gets replaced every 30k or so, unless they failed prematurely.

Yes, I agree that they would go lazy eventually, but if the engine is healthy, it would take a few hundred ks before you'll begin to see them going lazy. The only time I see them in need of early replacements would be the time when the exhaust stream sees a lot of garbage burned (additives), or engine burns oil (even pale oil/stoddard solvent, etc.)

Q.

 

[garlicbreadman]

Originally Posted By: PandaBear
I usually change mine when the smog check result is near failure at low speed (we put cars on dyno for smog in CA). They are easy to replace so at 200k I'd just replace it anyways.

I've used both Denso and NTK on my 97 Integra before, they both work great.


Did you notice an immediate gain in MPG once changed? Which one did you like better?

 

[PandaBear]

Originally Posted By: garlicbreadman
Did you notice an immediate gain in MPG once changed? Which one did you like better?


I didn't notice immediate gain in MPG, they weren't bad when I first replaced them at 150k, just preventive as my smog was near failing. I used a Walker generic which was a rebadge Denso and I spliced my own wires.

At 254k miles, I replaced my oil pan gasket so I looked at the Denso, they were covered with white stuff because of my head gasket leak (another story, already fixed), so I replaced it with a NTK rockauto closeout. The car stumbled for a while because I didn't reset the ECU correctly (just pulled ECU fuse) or I didn't clean the IACV correctly and left puddle of cleaning fluid inside. Then I reseted it again by disconnecting the battery terminals for hours and this time it finally did the trick of resetting the ECU. My guess is the last sensor got so contaminated that the ECU enrich or lean out the mixture so much, a new sensor wouldn't match the setting anymore.

edited

I think I might choose Denso because the sensor seems to be bigger and there was a drop in emission reading after the change (2 years later) compare to the past. The NTK one seems to keep the same number if not worse (high nox but low co and hc, which means lean burn) after the change and a head gasket leak, so I'm not able to conclude that it is the new sensor or other components worn out during the leak (i.e. the cat).

If I have to take a chance I'd feel more comfortable with Denso in this case.

original
But since I'm not testing the 2 sensors back to back I don't know which one is really better. I'd just pick the cheaper one between the 2.

 

[Leo99]

On my 2003 Corolla, I can monitor the O2 sensor voltages via a bluetooth OBD2 reader and Torque Lite app on my Android smartphone. Knowing what the voltages are is easy. Knowing what they are supposed to be will take a bit of research and learning.

Don't know if your OBD2 will output the O2 sensor voltages but if you have an Android, I recommend you spend the $20 for the reader and learn about how these sensors work.

 

[Quest]

Originally Posted By: Leo99
On my 2003 Corolla, I can monitor the O2 sensor voltages via a bluetooth OBD2 reader and Torque Lite app on my Android smartphone. Knowing what the voltages are is easy. Knowing what they are supposed to be will take a bit of research and learning.

Don't know if your OBD2 will output the O2 sensor voltages but if you have an Android, I recommend you spend the $20 for the reader and learn about how these sensors work.


That's a 96 integra we're talking about. Still on OBD-I.

I no longer cares about monitoring O2 sensors health RE: OBD-II, for if the upstream sensor (wideband, with heater element built in) is bad, CEL will light up; weak downstream O2 sensor will give you a CEL as well.

When that happens, you know your O2 sensor needs attention.

Just like I don't sit in front of a front-loading washing machine watching clothes tumble....

Q.

 

[garlicbreadman]

Originally Posted By: PandaBear
Originally Posted By: garlicbreadman
Did you notice an immediate gain in MPG once changed? Which one did you like better?


I didn't notice immediate gain in MPG, they weren't bad when I first replaced them at 150k, just preventive as my smog was near failing. I used a Walker generic which was a rebadge Denso and I spliced my own wires.

At 254k miles, I replaced my oil pan gasket so I looked at the Denso, they were covered with white stuff because of my head gasket leak (another story, already fixed), so I replaced it with a NTK rockauto closeout. The car stumbled for a while because I didn't reset the ECU correctly (just pulled ECU fuse) or I didn't clean the IACV correctly and left puddle of cleaning fluid inside. Then I reseted it again by disconnecting the battery terminals for hours and this time it finally did the trick of resetting the ECU. My guess is the last sensor got so contaminated that the ECU enrich or lean out the mixture so much, a new sensor wouldn't match the setting anymore.

edited

I think I might choose Denso because the sensor seems to be bigger and there was a drop in emission reading after the change (2 years later) compare to the past. The NTK one seems to keep the same number if not worse (high nox but low co and hc, which means lean burn) after the change and a head gasket leak, so I'm not able to conclude that it is the new sensor or other components worn out during the leak (i.e. the cat).

If I have to take a chance I'd feel more comfortable with Denso in this case.

original
But since I'm not testing the 2 sensors back to back I don't know which one is really better. I'd just pick the cheaper one between the 2.


thanks for the info. I bought the Denso off rockauto for 38 shipped. NTK was 28 shipped. I chose the denso after reading amazon reviews saying that is looks exactly like the oem oxygen. Go figure, it does say the denso unit is the oem replacement.

 

[zzyzzx]

Originally Posted By: Quest
Originally Posted By: Leo99
On my 2003 Corolla, I can monitor the O2 sensor voltages via a bluetooth OBD2 reader and Torque Lite app on my Android smartphone. Knowing what the voltages are is easy. Knowing what they are supposed to be will take a bit of research and learning.

Don't know if your OBD2 will output the O2 sensor voltages but if you have an Android, I recommend you spend the $20 for the reader and learn about how these sensors work.


That's a 96 integra we're talking about. Still on OBD-I.


1996 car that doesn't have OBDII??

Anyway, I used Bosch O2 sensors on everything except on a Toyota, where I use Denso. I have never had an issue doing this,

 

[Leo99]

Originally Posted By: Quest
Originally Posted By: Leo99
On my 2003 Corolla, I can monitor the O2 sensor voltages via a bluetooth OBD2 reader and Torque Lite app on my Android smartphone. Knowing what the voltages are is easy. Knowing what they are supposed to be will take a bit of research and learning.

Don't know if your OBD2 will output the O2 sensor voltages but if you have an Android, I recommend you spend the $20 for the reader and learn about how these sensors work.


That's a 96 integra we're talking about. Still on OBD-I.

I no longer cares about monitoring O2 sensors health RE: OBD-II, for if the upstream sensor (wideband, with heater element built in) is bad, CEL will light up; weak downstream O2 sensor will give you a CEL as well.

When that happens, you know your O2 sensor needs attention.

Just like I don't sit in front of a front-loading washing machine watching clothes tumble....

Q.


All cars and light trucks built and sold in the United States after January 1, 1996 were required to be OBD II equipped. In general, this means all 1996 model year cars and light trucks are compliant, even if built in late 1995.

You can treat the O2 sensor as some sort of black box and depend on the CEL or you can spend $20 and learn how it works and observe your car's O2 waveforms and compare them to normal operation waveforms.

Personally, I find learning about the O2 sensors and their system and the car's ECU a lot more mentally stimulating than learning about motor oil.

 

[gathermewool]

Originally Posted By: Leo99
On my 2003 Corolla, I can monitor the O2 sensor voltages via a bluetooth OBD2 reader and Torque Lite app on my Android smartphone. Knowing what the voltages are is easy. Knowing what they are supposed to be will take a bit of research and learning.

Don't know if your OBD2 will output the O2 sensor voltages but if you have an Android, I recommend you spend the $20 for the reader and learn about how these sensors work.


I'm not sure that monitoring voltages visually will give much good data. The voltage changes so quickly, that it seems like it would be impossible to see whether the lean/rich swings are occurring correctly or too sluggishly.

 

[Vikas]

you need oscilloscope or new faster CAN protocol if you are using live data from scanner

 

[Number_35]

[/quote]

That's a 96 integra we're talking about. Still on OBD-I.

[/quote]

I think that all MY96+ in NA are OBD II.