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  #1  
Old 06-11-2007, 11:40 PM
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O2 Sensor Replacement Interval?

What is the replacement interval for O2 Sensors?

In this particular case I'm wondering if it's time to change mine in my M103, but I'm sure it's not too different most other FI Benzes.

The only rumor I've heard is 30k mi, but my books say nothing....

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Old 06-12-2007, 01:38 AM
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To the best of my knowledge the Oxygen sensor(s) should be replaced every 60,000 miles.
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Old 06-12-2007, 08:11 AM
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220 000 kms=140 000 miles.Third owner.
original o2 sensor,
passed emission test 2 yrs ago.

Is it time to change out the Oxygen sensor before the next emission test?

No dash lights has come on.
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Old 06-12-2007, 03:31 PM
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O2 sensors slow down with age.. To keep things running optimally I like to change them out every 30-40K.

I've also taken to updating our 3 wire O2's w/ 4 wire. Run the extra ground to the negative battery terminal and you'll have an O2 that responds quicker then the 3 wire.

Jonathan
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Old 06-12-2007, 08:00 PM
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Cool tip, Jonathan. I'll remember that.
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Old 06-12-2007, 08:33 PM
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Jonathan,

Do you have a Bosch # for the four wire? I need to pick one up ASAP, my only garage time for the next month is this weekend.

Thanks.
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Old 06-12-2007, 09:17 PM
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I am not sure that O2 sensor should be changed unless it stops to work. The voltage from the O2 sensor should alternate within a range (use AC voltmeter). If this is occuring, it is o.k., if it is pinned on low or high side, i.e. you see a constant voltage (use DC voltmeter because AC meter would read zero) then it needs a replacement. For eg. my car has >350K miles and it is the same O2 sensor. Had to replace the catalytic converter because that will clog over time.
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Old 06-12-2007, 10:21 PM
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O2 sensor replacement interval varies depending on the model and era. They come in 3 versions - 30k, 60k and 100k. Yours is probably a 60k - but the site below will say for sure. Periodically Bosch runs an advertising campaign on changing out O2 sensors periodically as a preventive maintenance item - on the grounds that fuel economy is improved. I have a tendancy to forget about it and replace it only upon an O2 fault code. But these days it wouldn't take much a fuel economy improvement to pay for a new sensor.

http://www.boschautoparts.com/Resources/VehiclePartFinder/
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Old 06-13-2007, 05:21 PM
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Quote:
Originally Posted by saumil View Post
I am not sure that O2 sensor should be changed unless it stops to work. The voltage from the O2 sensor should alternate within a range (use AC voltmeter). If this is occuring, it is o.k., if it is pinned on low or high side, i.e. you see a constant voltage (use DC voltmeter because AC meter would read zero) then it needs a replacement. For eg. my car has >350K miles and it is the same O2 sensor. Had to replace the catalytic converter because that will clog over time.
Never seen a more incorrect statement.
O2 sensors not only switch ( high/low ) voltage signal, but also switch at a certain rate.
This is called " Cross Counts ".
As a sensor ages, it will " slow down ".
When it reaches that stage, fuel economy and exhaust emissions generally suffer.
Maybe if you had changed your O2 sensor at say 100 k miles or sooner, who knows, may not have plugged your catalytic converter.
O2 sensors are a Maintenance item, i.e. part of a major tune-up.
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Old 06-13-2007, 10:01 PM
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It may be a mantainence item BUT in my 350K, not once did the O2 sensor light indicate to me that the O2 sensor was bad. And not once did the car fail an emission test. Just lost power gradually likely because of oil burning, and inspite of continuously degrading CAT, the emission was just fine. Plus when I tested the sensor output, it did modulate the output between 0.1 and 0.9V that mercedes manual says is a test for a good O2 sensor. At the same time I agree that the rate at which the O2 sensor responds to changes in oxygen is critical, and if this response rate is not adequate then the output of the oxygen sensor will not be accurate and the computer will make an inaccurate mixture adjustment. BUT if the lag is too big, at some point the O2 sensor output will go out of the limits. And if the voltage remains in the correct range, I am not sure if the problem is that significant.
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Old 06-13-2007, 10:10 PM
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What model year is your car ?
I bet you will not get away with it on an OBD II compliant ( 1995 + ) car.
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Old 06-13-2007, 10:18 PM
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87 260E. It does not have onboard diagnostic computer. On a car with OBD II, I assume it is much simpler because the computer will tell you when the sensor goes bad and perhaps the test that the OBD system conducts now is a more stringent test than what MB was doing in older cars. But it is also a fact that the old test was adequate because the emissions from my car were just fine.
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Old 06-13-2007, 10:24 PM
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As stated above, if you had changed your O2, chances are your cat would have lasted longer...a slow/wonky O2 is Very hard on your cat.

The early MB O2 lights were crude @ best...are you sure the light even works???

All the catalytic converter manufactures want to see you changing O2's @ 30-40k. Also, if you install a new O2 and don't' install a new O2 your warranty is voided.

Jonathan
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  #14  
Old 06-13-2007, 10:35 PM
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The O2 light came on with all other lights and went off normally, so there was no reason to believe that it was mal-functioning. Maybe a CAT would last longer if O2 sensor is replaced routinely, but it is unlikely in my case, because the car was burning lot of oil, so at some point the CAT was going to clog. The O2 sensor and even the clogging CAT as far as I can tell were doing their job just fine because the mixture was producing emissions well within the range. It is also possible that the O2 sensor on my car was an exception rather than the rule.
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Old 06-13-2007, 10:41 PM
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Quote:
Originally Posted by saumil View Post
But it is also a fact that the old test was adequate because the emissions from my car were just fine.
Sure, ....life was simple in 1987.
Todays cars produce emissions that are about 1/10 th of what they were 20 years ago.

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