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gas guage or fuel consumption?


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do not use the generic autozone "bosch oxygen sensor" IT IS NOT reliable... I'm using one and having the same problem... i have about 160 on this tank and its showing that I have a quarter tank I know I can't have used that.. since I'm on a roadtrip I'm gonna stop at the autozone down here and swap out the o2 sensor and get some chevron with techron fuel additive.. so I will update you when I get home

 

 

xoomer

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is the sensor easy to get at?

 

there are 2 sensors, one in front of the cats and one after the cats. the cheaper bosch ones look identical to each other, but one has a 3 plug and one a 4 plug. i've never seen a subaru unit. i've seen 4 total, all bosch.

 

i sprayed mine with pb blaster, and had npo trouble. some one wrote about warming up the exhaust, but i did mine cold.

 

john

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what is pb blaster and is the first o2 sensor a 3 plug or 4 plug?

it's a penetrating oil for rusty bolts and things. guys here swear by it. but almost anythig will help.

 

i don't remember the plug, but it you order the front one you'll be good. call subaru genuine parts, get it online. (do a search) (at places like autozone they will talk about bank 1 sensor 2, but subaru only has 1 bank and 2 sensors.)

 

the wiring connector for the front one is on the passenger side near the fire wall, i think. the connector for the rear one is on the left side of the trans about half way back underneath. i had toruble with this connector. it was hard to disconnect. even after i had worked with one out of a parts car. too much road dirt i guess. the front one i didn't change.

 

i put in used because i already had it. but based on conversation here, i'd buy oem online and use that. i don't know the quality difference but they all cost about the same. autozone 102$, subaru genuine parts, online 80$?

 

john

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ok i went out ot part source and called subaru and a bosch ( i know some of you guys said they were crap) sensor was 139 bucks and i called subaru and it was 260 dollars for a genuine part....thats a bit steep....this is in canadian dollars but we arent that far off from the american dollar anymore.....i just want to make sure that it is the o2 sensor before i buy anything.....im getting about 400kms per tank about 240 miles....there is soot in my tail pipe and i added fuel additive and there is no difference.....so im assuming right in thinking its the o2 sensor?

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You say you have soot in the tailpipe, so that sounds like it is running rich, alright. But before swapping out the O2 sensor, check the coolant temperature sensor. If it is not working, or the connector corroded, it will never signal the ECS to go into closed loop mode, so it never uses the O2 sensor. Sort of like the choke on a carb being stuck on, it makes the engine run rich and get rotten fuel consumption

 

Easy to check, and way cheaper than a new O2 sensor.

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There are two coolant temp sensors on the coolant manifold under the intake. The single wire one is for the gauge on the dash. The 2 wire one is what the ECU uses. If it fails totaly, the computer will throw the fans on all the time. If it gets corroded, it will just read cold.

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It's the one pictured in the autozone link that robm posted.

 

Yes, it will screw with your milage.

 

Look under the back of the passenger side intake manifold, and you should see the sensor. Usually a brownish plug.

 

With the right socket, you should be able to swap it out by only taking off the plastic intake from the air filter and the PCV hoses. 1/2 hour job for the inexperienced.

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but i think its working fine because when i first turn on the engine when its cols my idle is 1200rpm but when it warms up it goes down to 650rpm wouldnt that mean its working?
Coolant Temp does not screw with your gas mileage. Yours is working just fine. Get a new O2 sensor and stop dragging this thread on and on. Try some stuff out first before you go and just post more and more. Search some before you just keep going on asking questions. Coolant Temp and O2 are things even a total novice can do - you don't need to keep asking questions. Go to the parts store, ask for the part, buy it, put it on, it's that simple. We don't need to keep dragging on a thread about Coolant Temp and O2 sensors.
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lol, not always, what im wondering is, are the fans running all the time? Or they come on every once and while? RUnning cooler off course is not as effecient, but ur overheating lol. But o2 sensor is a good bet lol, im local bud, but i suggest u drive out the Missasauga Subaru, i love that dealer :D.

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