Replacing my 215k mile O2 sensor with a 120k mile O2 sensor?

[harrymaneuvers]

This weekend I was pulling parts from a 97 LSi sedan. Besides getting everything I wanted (antenna mast, tweeters, cup holder, jack handle, and more) ... I also happened to snag her 02 sensor for $5. My car has 215k miles on it (and I would bet the original O2 sensor too) but has never thrown a CEL for the O2 sensor.

The LSi overheated to the point where it warped the block and toasted the engine.

My first question would be... how much damage would that do to the O2 sensor that I pulled from that engine?

Second question would be: Should I attempt to clean it??? It doesnt look horrible... just a slight grayish tint to it.

Third question would be: With all of that said... do you think there is any advantage to putting in this O2 sensor??

[chuckthefuk]

My first question would be... how much damage would that do to the O2 sensor that I pulled from that engine?
-- o2 Sensors are designed to take extreme heat.. sure the motor overheated but that doesn't mean the motor was throwing fire balls. The engine wasn't properly cooled thus it overheated, it probably increased EGT (exhaust gas temp) but not to the point that it could harm the sensor.

Second question would be: Should I attempt to clean it??? It doesnt look horrible... just a slight grayish tint to it.
--You could clean it but really its only carbon build up. Grease, oil, coolant, gasoline just burns off and turns into carbon which will eventually bake on. Some people suggest heating the tip up with a propane torch then cleaning it with a wire brush but really this over kill.


Third question would be: With all of that said... do you think there is any advantage to putting in this O2 sensor??
-- Not really.. sure the o2 sensor has less mileage but your o2 sensor is working fine. If you have no CEL then you shouldn't worry.

-Chuck

[Huffer]

Overtime the sensors degrade from constant use - a lower mileage one may or may not be better depending on it's life. You really can't tell. Plus, you don't know if it works unless you test it for current.

So, you could keep around until your existing sensor gives up the ghost, but I wouldn't install it.

When it comes to O2 sensors, I always go brand new.

[green97gt]

do you think there is any advantage to putting in this O2 sensor??

if its not broke.....

...dont fix it.

[harrymaneuvers]

Can the O2 sensor reading be just slightly off enough to have the ECU compensate without throwing a check engine light?

Meaning... When an O2 sensor gets used... eventually it will start reading different from what it did on day one. So the ecu starts to compensate little by little until the varience is too much and it throws a code. Right?

Or does the CEL throw a code once the 02 sensor reads ANYTHING other than what it did out of the box??

Could the amount of use that my o2 sensor has be causing my engine to run rich/lean without throwing CEL 02 sensor code??

[chuckthefuk]

I am pretty sure the ECU reads the o2 readings within a range. So when the o2 sensor starts giving readings that are bellow or above the defined range then it will throw a code.
-Chuck

[Huffer]

I am pretty sure the ECU reads the o2 readings within a range. So when the o2 sensor starts giving readings that are bellow or above the defined range then it will throw a code.
-Chuck

Yep!

[harrymaneuvers]

So within that range... is the ecu compensating more and more as the carbon build up (or whatever ages the O2 sensor) increases? Until it reaches a point where it throws the code...

Or is everything operating exactly the same whether the o2 sensors signal is at the bottom of the tolerated variance or at the top of the variance?

My judgement would say that the ecu would be adjusting things until it reached the max tolerated varience. At which point it would throw the code.

Am I wrong?

[chuckthefuk]

EDIT/UPDATE:
I would do more research but the o2 sensor system in our cars is not for self-ecu tuning. Its there to measure the amount of emission coming from before and after the cat. The range were talking about is the tolerance level that the ecu is programmed to accept. The first o2 sensor closest to the motor is measuring and sending results to the ecu, the second o2 sensor is strictly monitoring the emissions level. The first o2 sensor does allow the ecu to adjust the air/fuel mixture but not at a "tuning" level.

So when you get a CEL its probably from a faulty sensor or extreme fouling of the sensor.

The concept of a wideband o2 sensor compared to the oem narrowband is simple the the o2 sensor is able to read a larger range. This is useful when using a air/fuel controller or programmable ecu to read how lean/rich (amount of fuel) your running and make adjustments through tuning.

So basically to answer your question... Yes the new sensor would probably be more "accurate" within the range and probably give you a "little" bit more fuel economy but its not even close to a brand new sensor.

Cheers
-Chuck

[ouch1011]

To answer the question of whether an o2 sensor can be bad without setting a check engine light, the answer is absolutely yes.

Without going into extreme detail, a standard o2 sensor is calibrated to output a voltage of 0.45V when the air/fuel ratio is stoichiometric, which is 14.7parts air to 1part fuel. That is considered to be the best compremise for the various controlled engine emissions, as well as a good balance between power and economy. But, because the engine computer can't reasonably react fast enough, and the cat convertor works best with a constant mix of slightly rich and slightly lean, the o2 constantly switches above and below .45V, or "rich" and "lean" respectively.

1 common failure of an o2 that might not cause a cel is if the o2 is lazy. That means it is switching too slowly, and reacting to the changes in exhaust oxygen content too slowly. Eventually the pcm will detect this, but if it is a little too slow, it may impact your economy and emissions without setting a cel.

Another failure that might not set a cel is if the o2 sensor gets contaminated. Usually this will cause the o2 to be completely inoperative, but it can also shift the o2 sensor readings, and cause it to output lower voltages than it should, which would cause the engine to run rich.

That being said, I don't know if replacing your o2 with another used o2 would be beneficial or not. My concern would be given how the old engine failed, if any coolant got into the exhaust, it will have destroyed the o2. Coolant contains silica. When this hits the o2, it coats the o2 and effectively insulates it from the exhaust flow.

So there is way more info then you probably ever wanted to know.

[harrymaneuvers]

Perfect!!! That is what I thought.

To simplify:

Even if your engine isnt throwing a CEL code, if your current O2 sensor is on the way out, and you replace it with a new sensor, you could potentially get slightly better fuel econemy.

What is the longest someone has heard of their car going on the original O2 sensor??? I am nearly positive I have the factory O2 sensor in mine and it is over 215k miles. I am thinking it is time to change it even if it isnt throwing me a code.

[chuckthefuk]

I am at 371,000km on the original sensors.
EJ22E
-Chuck

[harrymaneuvers]

Well doing the conversion... I am at 346,000 Km... EJ22E also!!!

[ouch1011]

Back in the days of fuel injection with really primitive diagnostics systems, many manufacturers would have indicators set to turn on at a predetermined interval to check or replace the O2 sensor. Typically it was at 60-80k intervals :) .

Its not unheard over for an O2 to last that long. I replaced one the other day that only had about 160k on it, but it was in a 91 Taurus, and it had just recently stopped working.