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#1 2013-01-10 10:18:01

Moto
Member
From: Grand Forks & EGF ND/MN
Registered: 2012-03-09
User Number: 7120
Posts: 238

Rear O2 senseor really likes to stay in the DP

I'll probably post a picture later, but to put it simply my o2 sensor fused to my downpipe.  When I tried to get it out it just broke off out of the down pipe (part of the stock DP broke off). facepalm  Probably should note that is soaked in PB blaster and liquid wench for 24 hours before I attempted to remove it. I heated around it a little before I made an attempt at it.

Later I tried to cut the threads free.  I have or have nearly cut through the outside of the female part that twisted off two different places... Still stuck  unamused

A new O2 sensor is on it's way but the forecast changed from 2 inches of snow to 9 so I would sort of like to get this thing running before the weekend. My Mazda isn't exactly great in the snow.

Any ideas?  From what I have read you don't really want to run without the rear O2 sensor on our cars.  Has anyone ever done it? (Car would be running a stage 2 map) It would only be run for two days in town, but it is going to be cold this weekend.

So the lesson of the day... If you have a higher miles Saabaru and you plan to swap DPs you might want to just order an O2 sensor at the same time. It could end up saving your stock DP. Supposedly O2 sensors have a life span of 110K miles anyway, but I have never seen one fail on any of my cars and I have a lot more miles than that on all of them. 

The OEM replacement is about 130 bucks.  If anyone cares the part number is 22690AA520 (For All 2003-2007 Impreza WRX & STi Manual Transmission Models).


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#2 2013-01-10 10:34:02

bentmettle
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From: Ann Arbor
Registered: 2005-11-16
User Number: 897
Posts: 2401
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Re: Rear O2 senseor really likes to stay in the DP

I ran with mine not really in the exhaust flow- and it's a seemingly popular thing to do.

It's just going to throw a code.  The ECU is only adjusting F/A based on the sensor before the catalytic converter.  The ones downstream are to determine if the converters are doing what they're supposed to.


What's the opposing theory?  Maybe there is something going on that I'm not aware of, but it doesn't jibe with the whole "put the sensor out of the exhaust stream" thing that everyone does with the higher flow DPs.

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#3 2013-01-10 10:35:07

krazykarguy
Worst ninja editor, ever.
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From: South of North Carolina
Registered: 2007-04-06
User Number: 1944
Posts: 8724

Re: Rear O2 senseor really likes to stay in the DP

In my '94 Honda Civic, the O2 sensor in the stock header refused to come out when I installed a tubular header on the car. So I feel your pain. You tried using an O2 sensor wrench, while the DP was still on the car, right? If it's not still on the car, you're probably wasting your efforts as your torque is being used to rotate the entire DP and not the O2 sensor.

It's not totally common that this happens, but considering that the O2 sensor in our DP is in a high heat cycle area, and is mounted nearly vertically, it's not as unlikely to occur.


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2014 Ford Mustang GT Premium 6MT - Sterling Gray Metallic - 475hp of crowd munching fun

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#4 2013-01-10 11:22:10

Moto
Member
From: Grand Forks & EGF ND/MN
Registered: 2012-03-09
User Number: 7120
Posts: 238

Re: Rear O2 senseor really likes to stay in the DP

Please disregard statements above.  lol  We have magic people that work in our machine shop  (helps to have the right equipment.)  Tossed the old O2 sensor in a small lathe and shaved it down until we could see the back thread.  Then he managed to get the rest off without harming a single thread on the old sensor.

I will probably install the new one when it comes anyway since this one has a bunch of crusty shit on it.

What's the opposing theory?  Maybe there is something going on that I'm not aware of, but it doesn't jibe with the whole "put the sensor out of the exhaust stream" thing that everyone does with the higher flow DPs.

Your boost target will supposedly be about 1 PSI lower and the car's A/F ratios supposedly get screwed up.  You may want to go look for information.  I couldn't find a lot, but people who tune the car said that it was a bad idea.  Apparently on the 02-03s it was OK...?  I looked for quite awhile last night.  There where quite a few people adding their 2 cents without knowing what was going on, but it might be worth looking into. Something about open and closed loop stuff.  I didn't really look into it too much.  The consensus just seemed to be that you shouldn't do it on 04s or newer.

After doing all this I just hope the one in the UP pipe doesn't go to hell.  As I expect the one in the UP might break off too and that looks like a real bitch to try to get out of the car.

Last edited by Moto (2013-01-10 11:34:10)


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Admin: http://kizashiclub.com ...and a crap load of other sites.

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#5 2013-01-10 11:36:03

bentmettle
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From: Ann Arbor
Registered: 2005-11-16
User Number: 897
Posts: 2401
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Re: Rear O2 senseor really likes to stay in the DP

I'm all back to stock, so I probably won't research too much.

Amusingly, when I went to pull the 02 sensor from the sparkplug spacers, I had one get stuck, and had to turn the sensor on the lathe, too, to get the sleeve off it.  Same exact thing.

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#6 2013-01-10 18:47:58

Jerm
Shibby
From: Kingsport TN
Registered: 2012-07-22
User Number: 7458
Posts: 239

Re: Rear O2 senseor really likes to stay in the DP

I disabled the secondary o2 sensor, have had no issues.  I have no catalytic converters, so I don't see the need for it.

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