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Old 04-06-2005, 04:55 PM   #1
Al_Smokemcrack
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1997 Legacy Outback
Glacier White

Default O2 Sensor Woes

Went to change my O2 sensor last night. I'm thinking my crappy gas milage was related to the fact that it was the orignal 150k old sensor. But, it was fused on there. So bad, in fact, that when I broke it loose, I quickly realized that the sensor hadn't come loose but the bung had cracked clean off the cat. I'm going to take the cat off tonight and see about getting the bung welded back on. Torches and liquid wrench do wonders for stuck bungs, apparently.

Just wondering if this has happened to anybody else and what they did about it.
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Old 04-06-2005, 05:12 PM   #2
powerlabs
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Removed mine to replace cat converter @60K miles; threads stripped, found out new sensor costs $120+, re-threaded it and put it back on the new cat
Now I am running a wideband O2 through a wideband / narroband converter from PLX devices.
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Old 04-06-2005, 09:28 PM   #3
Al_Smokemcrack
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What advantages are there to running wideband sensors converted to narrowband? I know the widebands are more accurate, but don't you lose the precision when you deamplify it by five times?
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Old 04-07-2005, 02:44 AM   #4
powerlabs
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In simple terms:
I found it IMPOSSIBLE to tune my A/F Ratio WHATSOEVER without the wideband O2.
And it took me 4 WOT runs to tune it within perhaps 0.3% AFR with the wideband.
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Old 04-08-2005, 01:52 AM   #5
Al_Smokemcrack
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Okay. I still don't get why it'd make a difference, only that it seems to. Are widebands more linear, perhaps?
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Old 04-08-2005, 04:09 PM   #6
AJ711
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Look at it this way.

A narrowband operates between 0 and 1 volt, and not on a linear scale either. For the sake of argument, let us assume that it operates on a .1V incremental scale.

Take that same scale and apply it to a 0 to 5 volt range, and you'll be 5 times more accurate/precise in your readings of the Air to Fuel ratio. This makes it easier to tune with, as you have the ability to really nail the A/F ratio down to a single number.

As well, wideband do operate on a linear scale, where as narrowband are something far from linear. The scale helps in tuning as well, as there is not a large range of voltages which equate to 14.7 on the A/F scale, like narrowbands tend to do.

For daily driving, a wideband is overkill. If you want to tune your car yourself, a wideband is essential. The narrowband output from powerlabs's PLX device is no different from what your stock narrowband was supplying the ECU with, and the stock will cost a couple hundred less too.

AJ
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Old 04-08-2005, 04:57 PM   #7
Al_Smokemcrack
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Ah. So it's linear. I understand now. You use the actual 0-5V linear output from the wideband sensor itself to do tuning while you convert it to the more or less hyperbolic signal that a narrowband would have so it's compatible with the ECU.
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Old 04-08-2005, 05:40 PM   #8
AJ711
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Default

You hit the nail right on the head there.

Check out PLX Devices for more info on wideband kits. I use them as a reference, though there are other companies out there that have these types of kits. Powerlabs used one of PLX's (as mentioned above) and I like the features they provide.

Most kits will offer a "narrowband output" signal so you can keep your stock ECU. Some standalone ECU's (Hydra for example) can run directly off the wideband output, so the narrowband isn't needed. But then again, the Hydra has its own wideband kit that plugs right into it.

Back on topic: When you install the new O2 sensor, be sure to put anti seize on the threads, as it will greatly aid in getting it out the next time. As well, use some liquid wrench/WD-40/whatever to help get things out.

I was changing mine out a few weeks ago, and it wouldn't budge. Liberally sprayed it down with WD-40, let it sit for a bit (changed PCV valve, alternator/crank/steering belt, and swapped summer rubber on the front wheels) and it moved with ease.

If you're using the O2 sensor socket, try hitting the ratchet with a hammer or something. Human impact wrench to help break things loose.

AJ
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