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I have a 2005 Outback XLT Limited with the 2.5L turbo engine

and 118K miles. The...
I have a 2005 Outback XLT Limited with the 2.5L turbo engine and 118K miles. The engine began to cycle between surging and decelerating under acceleration. Then the "Check Engine" light came on and the surging stopped. The local mechanic read the fault code for an O2 sensor. Is it just a bad O2 sensor or could it be something up stream causing the air/fuel mixture to be wrong and throwing the O2 code?
JA: Does the light stay on, or does it blink?
Customer: Stays on. The Cruise control light is blinking.
JA: Are you fixing your Outback yourself? What have you tried so far?
Customer: I may give it a try if it isn't too complicated. My local mechanic suggested fuel cleaner - but that didn't fix it. The engine light came back on. He suggests replacing the O2 sensor.
JA: Anything else you want the mechanic to know before I connect you?
Customer: no.
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Answered in 8 minutes by:
11/22/2017
Gunvir Singh
Category: Subaru
Satisfied Customers: 1,853
Experience: Master Tech at Kennesaw Auto Tech
Verified

Hello, let me review your request. Please stand by.

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Do you have the check engin elight code number?

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Customer reply replied 19 days ago
No. My mechanic read the code and just said it was the O2 sensor.
Customer reply replied 19 days ago
I'm just wandering if other issues would throw this code, such as a MAF meter or vaccum leak. If only the O2 code is showing, is it wise to fix that first and see what happens?

This vehicle is equipped with narrow band oxygen sensor and will not effect driving or engine performance. Depending on the engine light code there is a possibility of an additional issue causing the engine surge and oxygen sensor to act up as well

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Customer reply replied 19 days ago
Should we look for other codes?
Customer reply replied 19 days ago
sometimes the engine runs fine, even with the CEL on.
Customer reply replied 19 days ago
If I understand you correctly, on this engine the O2 sensor does not change the air/fuel mixture. So if it is faulty, it wouldn't affect engine performance. Is that correct?

If there was additional codes present the mechanic would have seen them. There are other reasons for the symptom you are experiencing like a vacuum leak, faulty mass air flow, low fuel pressure or something as simpke as a tune up. A faulty oxygen sensor can definately trigger the checl engin elight but cannot cause an engine surge.

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I just checked and this vehicle is equipped with narrow band oxygen sensors and should not affect the air fuel ratio.

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Customer reply replied 19 days ago
Do you suggest checking for air leaks or looking at the MMAF first?

Depending on the code, if it says straight up that the oxygen sensor is faulty then i will recommend to replace the sensor and then check for further codes but if faulty oxygen sensor is only one of many possible causes for the code present then start by checking other possible causes like vacuum/exhaust leak, faulty mass air flow, throttle plate dirty or engine due for tune up.

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Customer reply replied 19 days ago
Ok. Thanks.

You're welcome and good luck with your vehicle, And please don’t forget to rate my performance in the upper left corner otherwise i don’t get compensated. Thank you and have a blessed day.

Gunvir Singh
Category: Subaru
Satisfied Customers: 1,853
Experience: Master Tech at Kennesaw Auto Tech
Verified
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