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Old 07-08-2005, 12:46 AM   #1
OBWagonWheels
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Outback Sport Soot in my tail

Its not what you think. I walked up behind my 2001 BE and noticed soot in and on the end of my exhaust tip. I seem to remember reading a thread that suggested that this is a sign of a O2 sensor gone bad. Am I recalling this correctly? My local mechanic said that he checked my O2 sensor when I did my 60K service last month, but I am not sure how he checked it or what that really means. I am guessing that it is the front sensor that the thread was talking about and not the A/F sensor. Seems a lot of problems are caused by this sensor.
-Neil
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Old 07-08-2005, 03:34 AM   #2
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yeah if there's a huge buildup(irregularly large) you should probably get it checked out again.

if they did a check up and you think they missed something, ask them about it and you might just be right.

it would be the front O2 sensor, you're right about that. the cat efficiency sensor doesn't have anything to do with the ECU's fuel adjustment.
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Old 07-08-2005, 07:10 PM   #3
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How much are we talking here?
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Old 07-08-2005, 08:36 PM   #4
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Well the exhaust tip is black about 2 inches up the outside of the tip. Seemed like a lot to me.
-Neil
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Old 07-08-2005, 10:01 PM   #5
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Wipe it clean and check it after a day. If you have more than a small ring arond the tailpipe, you may be needing a new O2 sensor. Hows the milage been lately?

Jay Storm
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Old 07-08-2005, 10:39 PM   #6
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Been getting about 18-19mpg, but that includes some freeway driving. Not very impressive. The car has about 6ok miles on it and I added a Cobb CAI 2 months ago. I'll clean off the tip tonight and recheck in a day or two.
-Neil
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Old 07-09-2005, 03:21 AM   #7
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18-19mpg? You've probably got a bum sensor making you run pig rich. Check the exhaust for a confirmation to see how quick it gets sooted up....but my money is on a bad sensor...


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Old 07-09-2005, 05:23 AM   #8
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Does the A/F sensor ever go bad?
-Neil
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Old 07-09-2005, 05:28 AM   #9
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the MAPs are usually pretty good about not crapping out...
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Old 07-09-2005, 07:06 AM   #10
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I didn't realize that the MAP is the air fuel sensor. I thought I had this figuesed out, but I guess not. Are there only 2 O2 sensor, and are they just befor and just after the cat?
-Neil
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Old 07-09-2005, 11:47 AM   #11
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Quote:
Originally Posted by OBWagonWheels
I didn't realize that the MAP is the air fuel sensor. I thought I had this figuesed out, but I guess not. Are there only 2 O2 sensor, and are they just befor and just after the cat?
-Neil

Yep. The one prior to is the only one that would matter in your situation. The other one is for cat efficiency and from what I have seen, it will throw a CEL if it goes bad.

19mpg sucks. I'd be figuring something out soon. even when I have the occasions to "drive it like I stole it" I still end up with at least 20mpg CITY.

Jared
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Old 07-28-2005, 08:34 PM   #12
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So, I replaced my pre-cat O2 sensor, and no more soot. Gas mileage didn't change much, though. I drove from San Francisco to LA and back. I got about 22-23mpg. That was in 110 degree heat with the AC full blast @ about 80mph. I still get about 19mpg around the city. Maybe that isnít so bad, but I have of people getting better mileage. I might need lighter shoes.
-Neil
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Old 07-28-2005, 11:08 PM   #13
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That's about right. You do drive a brick ya know....

Glad you got it figured out.


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Old 08-25-2005, 01:21 PM   #14
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Forgive me father, for I have sinned. It has been one month since my last post. I have gone through 4-5 tanks of gas and still am getting about 19mpg with mixed freeway and city driving. I have even gotten lighter shoes for my right foot without any help. My mechanic suggested taking the car to a dealership since they "have the right equiptment to potentially diagnose the problem." When I asked him whether increased drag on the drive train could be the problem, he stated that it was unlikely, and that more then likely it would be an enjine related issue. Any advice?

He also thought that I would spend more money looking for the problem then it would cost to buy the extra gas. He is obviously not much of a tree hugger.
-Neil
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Old 08-25-2005, 02:34 PM   #15
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How about these obvious maintenance things: new air filter and plugs? You got you tires aired up right? Do it run/idle poorly? Carrying around a ton of crap in the trunk? You mileage is pretty much the same as mine- 19-20 avg.

FWIW, I did do a little better than you on my last SF-LA trip, 23.5-24.5, ac on, 2 bikes on the roof, 75-80 the whole way.
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Old 08-25-2005, 05:06 PM   #16
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Wow, my first tank of gas i had a super heavy foot and only pulled out 20mpg, but i my spark plug boots kept coming off and i was dumping alot of fuel through the cat. Since then, i still drive pretty hard and 1/2 of my miles are highway and the rest are city. and i get 25 mpg. I think 20 is way too low..
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Old 08-25-2005, 11:36 PM   #17
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Quote:
Originally Posted by mrpedal
How about these obvious maintenance things: new air filter and plugs? You got you tires aired up right? Do it run/idle poorly? Carrying around a ton of crap in the trunk? You mileage is pretty much the same as mine- 19-20 avg.

FWIW, I did do a little better than you on my last SF-LA trip, 23.5-24.5, ac on, 2 bikes on the roof, 75-80 the whole way.
I added a Cobb CAI about 2 months ago, and changed the plugs to iridium plugs at about the same time. My tires are kept at 38/36. I have a Thule roof rack with a small fairing and two bike carriers, a trailer hitch, rubber mat for the back, and a childs car seat (real chick magnet).

Where in the SF Bay are you? Do you know a good dealer? The closest one to me is either Walnut Creek or Fairfield, and I haven't been impressed with either one.
-Neil
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Old 08-26-2005, 12:23 AM   #18
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Well, you passed that quiz pretty well, such as it was. Nothing wrong there.

I'm Union Square-ish in SF. I have been taking it to Downtown Subaru in Oakland. They're ok I guess, just really friggin expensive. My first CEL I took it there- 110$ flat fee to pull the code. Since then it's gone up to $125. Ouch. The service has been really good, but no real hmm... cost saver/friend type answers, just the "Part x is bad, it will cost $73829120.48 to fix it". I'm just being cheap. They did everything they were supposed and well.

Not sure if that was a glowing reccomendation.
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