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Old 01-22-2020, 09:00 AM   #1
TheVolvo966
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Default Oxygen sensor

Here’s a random question I had: is there anyone that changes their o2 sensor at a time/mileage interval?

We know they wear out and get “lazy” at a similar rate to modern spark plugs, but I have never seen (other than “boost your fuel economy” posters) a recommendation from an OEM how often they should be replaced. For many, they just get replaced when the CEL comes on but I was wondering if anyone here has thoughts / does this as part of routine maintenance for your daily?

Might be overkill but thanks in advance for your thoughts..
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Old 01-22-2020, 09:06 AM   #2
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One reason to change a sensor before it fails is it might become one with the pipe or converter after so many years in some environments. Like in Illinois.
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Old 01-22-2020, 11:44 AM   #3
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Originally Posted by cleanflametrap View Post
One reason to change a sensor before it fails is it might become one with the pipe or converter after so many years in some environments. Like in Illinois.
Good point, the rust is brutal here! My downpipe is stainless so I don’t think that will be an issue
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Old 01-22-2020, 12:21 PM   #4
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Good point, the rust is brutal here! My downpipe is stainless so I don’t think that will be an issue
Right. Sometimes the sensor bung is too, I guess, but not in my experience.
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Old 01-22-2020, 12:40 PM   #5
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Bosch has recommended service intervals for their O2 sensors. Mileage depends on type of sensor. I THINK for these 3 wire pieces it's listed as 160000km/100000mi.

EDIT: Just looked it up to confirm. The numbers above are correct.

Last edited by shoestring; 01-22-2020 at 12:52 PM..
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Old 01-22-2020, 02:55 PM   #6
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Originally Posted by shoestring View Post
Bosch has recommended service intervals for their O2 sensors. Mileage depends on type of sensor. I THINK for these 3 wire pieces it's listed as 160000km/100000mi.

EDIT: Just looked it up to confirm. The numbers above are correct.
Ah okay this is good info! I was also curious if any of the TB guys replaced them at their own interval? Like “every 3 years” or so?

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Right. Sometimes the sensor bung is too, I guess, but not in my experience.
I believe mine is as well? I can’t remember now but I think the whole assembly is stainless.. at least I hope so
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Old 01-22-2020, 03:38 PM   #7
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I'm not much on practicing prophylaxis on our family fleet of 240s in general, preferring to wait for failure so I can practice diagnosis, so maybe my advice is not so helpful to your question. I've had enough failures, though, that I can say I've been able to remove every failed oxygen sensor (and spark plug for that matter).

But, I've been hanging around the forums for 20 years and have read of many struggles getting lambda-sonds out of old converters and headpipes. Same with spark plugs. The metallurgy doesn't tell the whole story even if you factor in SS's proclivity to galling.

Electrically, or performance-wise, the oxygen sensor's life depends on keeping it hot (heater circuit working) and uncontaminated (oil burning, sealants, coolant, etc.) and so is generally unpredictable, but yes, the maker does put a "safe" number on it.
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Old 07-29-2020, 07:52 AM   #8
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Hello,

I have an O2 sensor question myself. My 1987 245 has an O2 sensor on the exhaust manifold. It does not look like there is one anywhere else. I'm planning to have these https://www.kgtrimning.org/tuning-sp.../typ1-240.html installed professionally. These do not have an O2 bung on them and from what I hear the best place to have one installed is as close to but also downstream from where the four pipes collect together. Are all O2 wires the same? I ask because I do believe a longer wire will be needed and the folks who work on my car definitely prefer me to obtain the parts and give to them. All thoughts/comments are appreciated. Thanks very much.
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Old 07-29-2020, 09:43 AM   #9
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Quote:
Originally Posted by Fred Gwynne View Post
Hello,

I have an O2 sensor question myself. My 1987 245 has an O2 sensor on the exhaust manifold. It does not look like there is one anywhere else. I'm planning to have these https://www.kgtrimning.org/tuning-sp.../typ1-240.html installed professionally. These do not have an O2 bung on them and from what I hear the best place to have one installed is as close to but also downstream from where the four pipes collect together. Are all O2 wires the same? I ask because I do believe a longer wire will be needed and the folks who work on my car definitely prefer me to obtain the parts and give to them. All thoughts/comments are appreciated. Thanks very much.
I bought the above about 2 years ago and it wasn't even close to fitting. It seems like they built it assuming the trans crossmember didn't exist. just FYI

I did eventually have it modified and installed, and I installed the o2 right about where the header pipe ends. (and the rest of the exhaust begins)
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Old 07-29-2020, 10:21 AM   #10
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Originally Posted by esmth View Post
I bought the above about 2 years ago and it wasn't even close to fitting. It seems like they built it assuming the trans crossmember didn't exist. just FYI

I did eventually have it modified and installed, and I installed the o2 right about where the header pipe ends. (and the rest of the exhaust begins)
Thanks very much! I'm sick of having headaches so I will likely pass on these headers. Unless perhaps someone here has gotten a set since then and had no trouble installing then.
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Old 07-29-2020, 10:55 AM   #11
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Quote:
Originally Posted by Fred Gwynne View Post
Hello,

I have an O2 sensor question myself. My 1987 245 has an O2 sensor on the exhaust manifold. It does not look like there is one anywhere else. I'm planning to have these https://www.kgtrimning.org/tuning-sp.../typ1-240.html installed professionally. These do not have an O2 bung on them and from what I hear the best place to have one installed is as close to but also downstream from where the four pipes collect together. Are all O2 wires the same? I ask because I do believe a longer wire will be needed and the folks who work on my car definitely prefer me to obtain the parts and give to them. All thoughts/comments are appreciated. Thanks very much.
The O2 sensor is not like a thermocouple which requires matching metallurgy when extending the wires. A good quality wire with the appropriate wire gauge, temperature rated insulation and jacket will work fine. The best way to do it is to find the matching plug for the O2 sensor so that you can leave the existing sensor wiring intact and just extend from the existing plug.
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Old 07-29-2020, 11:04 AM   #12
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For my '95 945 I just replaced stock lambda connector with superseal 3-pole unit.

Some 240 lambdas are located at catalysator, and they have long wires.
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Old 07-29-2020, 11:14 AM   #13
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Like Bosch 0 258 003 308, the wires are over 5 ft and inches. And connectors are direct fit, i guess.
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Old 07-29-2020, 11:21 AM   #14
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Quote:
Originally Posted by Fred Gwynne View Post
Thanks very much! I'm sick of having headaches so I will likely pass on these headers. Unless perhaps someone here has gotten a set since then and had no trouble installing then.
i'd definatly ask around. Some other people seemed to have bought them and didn't report problems. Maybe they sent me one designed for a 7/9? BTW the stock O2 harness was long enough in my case.

Though if I were redoing my exhaust (which will be happening soon, due to the rust), i'd go with a coated stock B21F NA manifold with the O2 bung built-in and run the stainless downpipe from there. but i'm just benchracing now, haha
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Old 07-29-2020, 09:07 PM   #15
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Thank you all for your thoughts/comments! They are much appreciated.
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