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Old 06-17-2002, 03:34 AM   #1
ted109
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Join Date: Apr 2002
Location: Eugene, OR
Vehicle:
98 Outback Sport
Green

Default bad cat converter=horrible gas milage?

was driving back from portland, got a CEL. went and got it checked out and they said the catalytic converter was bad and needed replacing (phew, still under powertrain warranty). So the parts on order, they let me keep driving the car, say itl be fine. the CEL comes on again, and iv noticed that my gas milage is about half of what it should be. THe car also idles really rough. Is this from the converter? or maybe they reset the ECU in checking (would this do it anyways?), or is this an entirly unrelated problem? oh yeah, its a 98 m/t obs.

thx in advance,
Phill
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Old 06-17-2002, 10:35 AM   #2
Jademonkey
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You're probably running in "limp" mode...which runs the car really rich.
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Old 06-17-2002, 01:39 PM   #3
HndaTch627
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'09 Concours 14 ABS Black

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FWIW the catalyst is NOT covered under a power train warranty...as of right now it's coverend under and 8yr/80k mile warranty---emissons...and subaru will extend that later to include at least 10yrs or 100k miles per the government....as far as fuel mileage, if you had a cat that was clogging the exahust then yes...but 99 times out of 100 it won't affect it...you have another issue at hand...possibly a faulty O2 that's starting to get some slow response time.

good luck.

jeremy
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Old 06-18-2002, 12:18 AM   #4
ted109
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i dont think its running in 'limp home mode' cuz preformance isnt affected at all. did a few drags (eheh probly shouldnt have with the CEL and whatnot, but hey it was grad night), did as well as normal. 'possibly a faulty 02..', k, im a noob, but what does this mean? o2 sensor (maf?) or what?

thx again
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Old 06-18-2002, 03:29 AM   #5
HndaTch627
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'09 Concours 14 ABS Black

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bad primary(front) oxygen sensor
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Old 06-18-2002, 09:50 PM   #6
dodichi
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what kind of mods do you have on your car? because i have a MY01 2.5rs with 30k miles, i've already gone thru one catalytic converter. and i think this one is goning bad as well (rotten egg smell when i drive on the highway)
mods: cobb intake, stromung exhaust (stock midpipe)

does anyone have any idea why i keep burning cats?

thanks,
ed
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Old 06-19-2002, 12:59 AM   #7
ted109
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yeah, as far as mods...i made an iclub sticker and stuck it in the window;-). that had to add at least 5hp. dunno, some minor groundwork (in prep for a soundsystem if i ever get some cash).
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Old 06-19-2002, 02:21 AM   #8
HndaTch627
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Quote:
Originally posted by dodichi
what kind of mods do you have on your car? because i have a MY01 2.5rs with 30k miles, i've already gone thru one catalytic converter. and i think this one is goning bad as well (rotten egg smell when i drive on the highway)
mods: cobb intake, stromung exhaust (stock midpipe)

does anyone have any idea why i keep burning cats?

thanks,
ed
well since they just announced a recall on the ECM programming i'm gonna guess it's from running the car overly rich at all speeds causing the cat to overheat and prematurely deteriorate...i get the rotten egg smell all the time, it's actually just the sulfur in the fuel, but it wouldn't be so bad if the ECM's weren't programmed to run so rich. I'll let ya know how the new ECM pogramming does because ia m taking it in tommorrow morning to get it re-mapped.

jeremy
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Old 06-19-2002, 06:24 PM   #9
ted109
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where can one find info on this recall? like what models/years are under it n stuff. havnt heard anything cept from a few posts here.
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Old 06-20-2002, 09:03 AM   #10
MY99 2.5GT
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Your car has 3 cats but the O2 sensors monitor only the first one. I have a 99 with MRT Headers and the rear O2 sensor disconnected and running with no problems. Cat Efficiency Failure will not cause the ECU to switch to limp mode. Yes the Technician probably reset your ECU to clear the CEL. This would explain your bad mileage.

As far as front O2 Sensor Failure, I believe this would throw a different code then cat efficiency and may put your car into limp mode. The front O2 sensor in your car is a narrow band 0-1 watt sensor that is used to monitor the A/F mixture. One of its other functions is to monitor the temperature of the exhaust before it enters the cat among other things. That reading is then compared to the rear O2 sensors reading to see if the Cat is working. If your in limp mode I believe the ecu limits rpms to 4000(Please Correct me if I'm wrong). If you are in limp mode I would say Jeremy is probably right about the front O2.

Let us know what happens.

Brad
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Old 06-20-2002, 06:34 PM   #11
ted109
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well, they replaced the converter, CEL is gone. Car still rumbles a bit when idling (im assuming this is from the ecu reset causing it to run rich?). how many miles before the engine relearns its shiznit and stops ransacking my piggybank?
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