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Old 11-12-2008, 02:02 PM   #1
Scoobycharged
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Member#: 186646
Join Date: Aug 2008
Chapter/Region: MWSOC
Vehicle:
2000 Impreza RS
BRP

Default Removed 2nd Cat, No o2 Sensor

Today, I got my second cat removed and a custom pipe fabbed in its place. However, he didn't weld the bung back to re-mount the sensor so he just unplugged it and sent it back with me.

My question is, can my car run fine (aside from the P0440 code) without the rear o2 or am I going to need to put that back on?

Also, is there any way to make my 00RS completely catless? Because the front (the important one) sensor is plugged directly into the front cat. Can I just cut out the cat and weld the o2 sensor into a straight pipe? Will it give the correct readings?

I appreciate the help guys.
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Old 11-12-2008, 07:14 PM   #2
Scoobycharged
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bump. need some help.
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Old 11-12-2008, 07:39 PM   #3
my4isflat
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Legacy w/325k mi (RIP)

Default

The sole job of the rear O2 sensor is to monitor the cat. It serves no function for driveability or engine performance.

Yes, you can make your RS catless, you just have to weld in a bung so you can reinstall the air/fuel sensor (front O2 sensor).
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Old 11-12-2008, 09:01 PM   #4
RaceFaceXC
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2007 No YELLING
on the bus!

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the rear O2 on the 06-07 2.5i's (and 05's?) also does have some ECU input for fueling, in addition to monitoring the cat. its impact on fueling is minimal, but still has some. Id bet the 08 and 09 models will be similar. just thought id add this info for reference, in case future readers/searchers are looking for info on late models.
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Old 11-13-2008, 11:36 AM   #5
Scoobycharged
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That's really weird guys. After getting my new pipe fabbed up, I drove my car home (it was alright) then I drove it about 7 hours later for a 35 minute drive. The ENTIRE way there my car was extremely boggy at low speeds. It took like 2 seconds for the throttle response to really kick in. The only other thing I could think of, besides the o2 sensor, was I got water (it was really rainy, and we have ****ty roads) in my CAI. But, I'm pretty sure if that would've happened I would've "hydrolocked" and the car would've been dead.

Does this sound like anything? My car always runs top notch. Im Scurred.
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Old 11-13-2008, 08:54 PM   #6
RaceFaceXC
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COULD be the CL fueling is off causing "bogging", and after the CL/OL delay it will run fine in OL (no O2 sensor input) be interesting to see what would happen if you replaced the rear O2 bung and installed the sensor. if it fixed the problem, that would point to the rear O2 being involved in fueling. apparently it isn't involved at all on pre DBW impreza's, but this unique scenario makes one wonder.
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