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Old 12-31-2008, 08:37 PM   #1
tracky00
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Join Date: Aug 2007
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Location: Eugene, OR
Vehicle:
2000 2.5RS Coupe
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Default Front O2 Failure every 6-8mths

Ok so I'm getting kind of pissed. I have a 2000 RS that had a custom 2.5" header back exhaust with no cat. I replaced about 3 front O2 sensors on it due to failure, replacing them about every 6-8mths. I was guessing it was because of the crappy cat-less exhaust, so I bought a complete new exhaust in April. Borla headers, Stromung High flow cat, and a Stromung cat-back. Replaced all gaskets, and replaced the front O2 sensor with a Subaru sensor. Car sounds great and added some power, but wouldn't you know it my front O2 sensor has failed again! Does anyone have any idea why this is happening? I'm getting tired of spending $100 bucks every 6-8 months! I know I'm not the only one the has ran a cat-less or a high-flow exhaust. Has anyone heard of this happening before? What could be causing this? Please help.
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Old 12-31-2008, 08:41 PM   #2
Back Road Runner
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How is your car running? Rich?
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Old 12-31-2008, 09:02 PM   #3
Cocoa Beach Bum
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Old 01-02-2009, 01:09 AM   #4
tracky00
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I would definitely say it's running rich. How would I lean it out?

I will have to head down to Subaru to check on the reflash. I don't believe it's been done.
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Old 01-02-2009, 02:26 AM   #5
2.5i
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Yea the car is running to rich, thus putting more carbon on the O2 sensor. There could be a couple things that would make it run rich. Take it to a shop and have them diagnose the problem. You could run E85 in your car that would make it lean out, although I wouldn't run straight E85 unless you are tuned for it, and some would say not to run E85 at all until your car is tuned for it.
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Old 03-06-2009, 12:23 PM   #6
gdcwatt
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I'm here to learn about Imprezas, but since I'm here...I had a high-mileage (300,000km) 91 Civic Si which, during the last 4 years I owned it, had problems which I suspected were caused by the O2 sensor. Every six months, when it started to run rough, I'd spray half a can of throttle body cleaner into the TB, while working the butterfly valve, and the car would run great for another 6 months. Is this a cheap fix that might work for you? Is the MAF something that you have to work around, if this sounds like something to try? After 12 years I never replaced the Civic's 02 sensor.
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Old 03-06-2009, 12:56 PM   #7
Back Road Runner
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ECU tune can help a lot for getting the air/fuel more consistent. I-Speed has their flashes, and the air/fuel runs a little lean on them. You could take your car to a dyno that can work with OpenECU and let him tweak it for a couple hours to get something more consistent.
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Old 03-06-2009, 03:09 PM   #8
yarrgh
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if you're new here, I'd suggest starting a new thread for any questions. MAF sensors do need to be cleaned now and then.
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Old 03-09-2009, 02:17 PM   #9
Burnout
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Quote:
Originally Posted by Cocoa Beach Bum View Post
I second that. In short your A/F sensor is producing voltage that the ECU is not calibrated to.
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