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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Weird O2 Sensor



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      07-02-2016, 09:35 AM   #1
mecbain
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Weird O2 Sensor

K so you know those o2 sensors that are so hard to take off? well for some reason one of them on my car unscrews himself, no joke, has been screwed over quite a few times at the garage and a week or 2 afterwards it pops out again.

Now, this is not really a problem, because even more weirdly, the car is running much better with it not screwed in properly, by better I mean that it's like making 10/15% more torque between 1500 and 5500 rpm, it sounds much better too (from the actual muffler, not where the o2 sensor pops-out).

So why would an o2 sensor unscrew himself? Maybe caused by the drive terrain movement because of worn motor mounts? although the garage said they seemed fine, a clogged catalytic converter?

And than why is the car running so much better with an o2 sensor only half screwed in? Is it because it's detecting less air so it adds less gaz? Or it's not what's he's expecting, so it takes time to adapt to new readings?

Not really looking for a solution, as the car goes and sounds really good as is right now, so I guess I'll keep it like it is, was just curiuos to hear some of your opinions on the subject
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      07-02-2016, 02:20 PM   #2
Misty
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how is ur gas mileage when my o2 seconsor was giving me an SES light i was getting like 10mpg on my n51 e92
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      07-02-2016, 04:23 PM   #3
mecbain
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no change since the last 4 years...
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      07-02-2016, 10:44 PM   #4
hassmaschine
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Which O2 sensor? The post cat sensors don't affect the tune.

If its unscrewing you probably need to replace the sensor. Any perceived change in performance is coincidence - an exhaust leak will read as a rich mixture and cause it to lean out.
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      07-03-2016, 07:49 PM   #5
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I'll have to double check which one.

If it leans out than shouldn't that equal more power? I understand it's more complex than that but in general unless the leaner mixture produces other problems it should have more power no?


the behavior "increase in power" has been observed 4 times over a period of 1-2 years last 2 times being weeks a part, not really a coincidence

that's why I was wondering if the increase in power isn't due to the leaner mixture as i thought could it be simply because the cat is clogged

again just curious I really like how it runs right now no matter why so not complaining
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      07-03-2016, 09:47 PM   #6
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No, not really.
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