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Discussion Starter · #1 · (Edited)
So I have been tracking my mileage on my 2011 2.5 limited outback since march of this year (when it was purchased). Just within the last two months or so the range per tank has dropped about 100 miles a tank. During weather colder than 50 degrees I have rough idle, loss of power and mileage. Today I got to do more driving with above 50 degree temps and was able to get about 160 miles with a bit more than 1/4 tank used. Tonight temp dropped and I drove 30 miles and took almost 1/4 tank, rough idle returned and acceleration was seeming a task. I have an obd tool attached and have not seen any codes. Ignition timing this afternoon showed about 15 to 30 and learned ignition .5 and tonight timing showed about 38degrees. Is it possible the MAF to be failing without giving a code? I have tried finding this question before posting. My other 2011 2.5 limited outback that we had over three years never exhibited this issue. The mechanic without any diagnostic ( I asked them to do basic diagnostics) could only say it is a high mileage engine at 278k miles.
 

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Sounds like you have an air leak or your MAF is going faulty. How many g/s is it showing. Is it showing flow when the engine isn't running ?
 

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Discussion Starter · #3 ·
Sounds like you have an air leak or your MAF is going faulty. How many g/s is it showing. Is it showing flow when the engine isn't running ?
I have put a vacuum tester on it and it showed in the normal range. MAF is 11.76 or lower when it is cold out. This afternoon it read between 13 and 42. Not sure what the numbers are telling me. I will have to check tomorrow and see if anything registers when the car is off.
 

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2018 Outback 3.6R Limited 50th Anniversary
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Winter fuel.... I seem to see 50-100 mile range difference during the winter months. In summer I can get over 400. During winter months 350ish. 2018 3.6
 

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Well its not your MAF, spec is 2.5 g/s and you have 2.6 , so that not it. You have 14.5 ignition timing and spec is 14-16. MAP is spot on. Oxygen sensors are about right. So whatever's happening wasn't happening when you took the screen caps.
 

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Probably winter gas and spending energy warming up engine/drivetrain. I've attached a graph of my 2011 gas mileage since new. The x-axis is kinda crunched due to time but every low point on the graph was in January-February.

Slope Rectangle Plot Font Parallel
 

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Discussion Starter · #11 ·
Probably winter gas and spending energy warming up engine/drivetrain. I've attached a graph of my 2011 gas mileage since new. The x-axis is kinda crunched due to time but every low point on the graph was in January-February.

View attachment 530132
Love the graph. This is mainly a concern because my other 2011 2.5 was rock steady no matter the weather with or without warm up time. It stinks that two identical cars can act so differently. Also during the colder days the engine sounds like it is surging while my foot is steady on the gas to take off or maintain speed.
 

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2010 Outback 3.6R 2014 Legacy 2.5i
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1. long warmup time for FB motors
2. winter fuel
3. colder temps = more dense air = more fuel
5. cold car takes more effort to move
 

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During weather colder than 50 degrees I have rough idle, loss of power and mileage.
I think we're focusing too much on the fuel economy and not enough on the loss of power. More detail about what has and hasn't been changed on the car and when, with what, might give clues. A bit surprised that the rough idle isn't showing ANY codes. I presume that the rough idle and power loss extends well into when the car is fully warmed up and has been driven.
 

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Discussion Starter · #15 · (Edited)
Yes the rough idle does continue after car is warmed up.


I have replaced
pcv hose (it was old and cracked) / just before Christmas
spark plugs / factory ngk two weeks ago
air filter / basic air filter in November
timing belt with water pump (no documentation on when it was last done before I purchased) / middle of November.
 

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I have a CAI with a cone filter on my outback. It makes the bee extra angry when I floor it. I get this code when I haven't cleaned the filter for like 6 months or so.

When was the last time you changed your air filter?
I see it says you changed it in November, and you mention basic, have you tried a better quality one to see if that is the issue?
 

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Discussion Starter · #18 ·
I believe it was an STP filter from Autozone. I have not ever been one to use a more expensive filter so I am not sure what would make it better? What would be recommended?
 

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Outback 2011 3.6R Premium (sold Jan 22)
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Post catalyst fuel trim too lean probably means the ECU is adding fuel to compensate.

Do you have any holes/leaks in the exhaust system? Exhaust leaks can make the exhaust run lean.

Seagrass
 

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Idk, quality since the world took a collective dump has dropped quite a bit. Even for legends like Toyota, Honda and Subaru and Gates, etc. Another air filter is cheap, different brand and clear rhe code. Otherwise we have to ask why your fuel trim is in the negatives - i.e why does it think there is less air than there should be despite the maf reading normal at idle but not suckin wind at speed...
 
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