O2 Sensors - Considered a maintenance item BEFORE they throw codes?

[anom3]

Is there any benefit to swapping out the pre-cat O2 sensors if they are not yet throwing any codes?

I am asking because I have a set sitting down in the garage as I was able to get a really good price on a set a few months back and want to know if I should bother swapping my existing ones or should just wait until the ECU decides they are pooched.

I am at roughly 55k miles on a 08 E92.

[stevelp99]

I'd say unless you fell there's a problem, or you run your car quite hard I'd leave it alone. Thant said, Bosch recommends replacing at roughly 100k, sooner on 90s and older vahicles. I had to replace one just last week (33k) for reduced power, increased emissions, misfire and so on, the sensor just out right failed. It does require resetting the O2 adaption limit by the way.

Replacing a worn out o2 sensor can improve fuel mileage and performance as its working at optimum efficiency since pre cat O2 sensor is part of the system that determines air fuel ratio.

[anom3]

So I did this just now. I decided to swap the sensors.

Quite happy with the result.

The car feels much more responsive. Noticing quite a bit of difference in lower gears when I go WOT.

Car has 85k KM on it. The old o2 sensors were covered in black soot. Not sure if thats normal or not.

[kaede]

Originally Posted by anom3

So I did this just now. I decided to swap the sensors.

Quite happy with the result.

The car feels much more responsive. Noticing quite a bit of difference in lower gears when I go WOT.

Car has 85k KM on it. The old o2 sensors were covered in black soot. Not sure if thats normal or not.

Interested in changing mine too! It's not exactly an expensive preventative maintenance item and could have benefits! Which part number is it for the front sensors and how many do we need? Also. Did you go with oem or aftermarket? Thanks!

[anom3]

Depending on your millage, I highly recommend it.

Its all "butt dyno", but the difference is night and day in my case.

As far as the part numbers, realoem.com and find them on there, not too hard. You will need 2. The post cat ones do not affect the performance of the motor at all and are used strictly for emission "notifications".

I went with the BOSCH ones. Although they are the ones who produce the OEM ones for BMW so its essentially the same part, just cheaper. I bought them about 6-9 months ago off ebay as they were listed at a really good price.

One thing worth mentioning... I have read that its best to reset the o2 sensor adaptations once you change them. I did this. But you will need an ODB cable and a working copy of INPA to do this...

Originally Posted by kaede

Interested in changing mine too! It's not exactly an expensive preventative maintenance item and could have benefits! Which part number is it for the front sensors and how many do we need? Also. Did you go with oem or aftermarket? Thanks!

[VictorH]

Just replaced both of my pre-cat sensors. I'm at 91,000 miles and had error code on the passenger side bank.
Replacement part is Bosch 17039 which is OE equivalent made in Germany
Prices seem to be going up even though Euro is weak. Paid $109 for the first one and $125 for the second one (about a week apart).


http://www.amazon.com/Bosch-17039-Ox...ds=bosch+17039

[oolas3]

Originally Posted by anom3

Depending on your millage, I highly recommend it.

Its all "butt dyno", but the difference is night and day in my case.

As far as the part numbers, realoem.com and find them on there, not too hard. You will need 2. The post cat ones do not affect the performance of the motor at all and are used strictly for emission "notifications".

I went with the BOSCH ones. Although they are the ones who produce the OEM ones for BMW so its essentially the same part, just cheaper. I bought them about 6-9 months ago off ebay as they were listed at a really good price.

One thing worth mentioning... I have read that its best to reset the o2 sensor adaptations once you change them. I did this. But you will need an ODB cable and a working copy of INPA to do this...

Do you know what are the ramifications of not resetting the o2 sensor adaptations?

[anom3]

I do not have a precise answer :/

My gut tells me that after a couple hundred KM the ECU SHOULD adjust as the adaptations are constantly updated.

I have to be honest I am not 100% sure I reset the correct ones as inside the software its all german.

I reset 3-4 that said EGAS (assumed exhaust gas) and Lambda-... (there were 3 of these from what I recall).

Took the car out for a short drive again today... In my case the difference is seriously night and day. Throttle response is much more instant. Car sounds better too and I had a tiny bit of a lumpy idle before, that's gone now too.

Originally Posted by m3m3mr

Do you know what are the ramifications of not resetting the o2 sensor adaptations?

[Richbot]

Resetting adaptations will change the way the car responds too. This is a well documented effect. Don't jump to conclusions mat just yet.

[thekurgan]

I generally replace them before, and clear the adaptations.

[anom3]

Yep I know. I have reset my adaptations many times before. Fully, not just selecting a few here and there. This is different.

The best I can describe it is, since im 6MT:

Drive in 1st. Get the RPMs up high enough to throw it into 2nd.
Clutch, put the gear in, but wait till the RPMs drop (eg: not a normal shift, a slow shift).
Release clutch.

Normally before, the car would buck quite a bit.

It still does a little, but the revs jump up much quicker now.

Originally Posted by Richbot

Resetting adaptations will change the way the car responds too. This is a well documented effect. Don't jump to conclusions mat just yet.