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Discussion Starter #1
Hey all,
So my wife's 2011 Outback seems to have this acceleration issue. It seems more prevalent the hotter the weather is. What happens is after 1 to 1.5 hours of driving or say a 45 minute to an hour drive and then driving the car again shortly after, the car will not accelerate properly. If you tip the throttle more than 1/5th or so, the car bucks and will not accelerate. However, if you barely get on the throttle you can very slowly accelerate up to the desired speed. So pretty much keeping the vehicle under 2.5k RPMs.

The other day the situation got worse, and my wife informed me the car would not do more than 20mph.

I had it to the Subaru dealership last month for a check per the CVT extension, however after they kept the car for over a week, they claimed they could not replicate the issue. After getting it back, it was fine for about 2-3 weeks, but now the issue is back.

Any ideas? I really have no idea how they had the car for so long, and claimed to had made 2+ hour trips with no issues.
 

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03 H6 OBW & 06 WRX Sportwagon
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weird, seems almost like an exhaust restriction.

I think you are gonna need to find some way to demo the problem for a mechanic/service writer.
 

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2012 Outback 2.5 Limited
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Given that it seems to vary with ambient temperature I would check the intake air temperature sensor (part of the MAF sensor). If you disconnect the harness and look at the pins of the sensor then pin 1 is to the right and pin 5 is to the left. Connect multimeter to terminals 1 and 2. Observe and compare to the following reference values:

-4F: 16.0 +- 2.4 kohm
68F: 2.45 +- 0.24 kohm
140F: 0.58 +- 0.087 kohm

You could plot those values and create a temperature/resistance curve to get expected values at the temperatures you're measuring for. Cleaning the sensor with a special MAF cleaner spray would be the first thing to try if readings appear out of whack.

Also see: https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-air-charge-temperature-sensor
 

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2011 2.5 CVT with lpg
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Do check and clean your maf sensor. (Only use maf cleaner they say). I had a similar issue to you recently and the exposed maf sensor wire nearest the air filter was filthy. I used an electric contact cleaner spray first, then gently cleaned the wire with a contact cleaning brush. Be gentle, but these two exposed wires on our mafs are more like 1 mm metal square section bars and were much thicker than others I've seen.
 

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Discussion Starter #5
I'll check out the MAF, thanks! It's so bizarre that the issue doesn't show its face until around after that hour mark. Hopefully this is it. On a scary note, when my wife took the car to a Subaru dealership they pulled the car's history, seems the transmission had already been replaced once...

I wasn't a fan of the dealership she went to either. They tried claiming the car would need 4 wheel bearings soon, really at 80k? I have never heard of such non-sense. Then he tried to say the tires are shot, they easily have another 15-20k miles left of life.
 

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As an aside, the "owners" section on subaru.com allows you to create a free account, enter your VIN, and get the dealership service history yourself.

Also, mycarfax.com is another awesome free resource to create an account and register your VIN. It pulls not only the dealership history but also a lot of other data from repair shops, emissions inspections, registration, etc.

The wheel bearing comment does indeed sound iffy. The question is how they came to that conclusion if you don't have any grinding sounds. If they indeed checked with a caliper instrument and it's out of acceptable range then yes. If not it sounds like dishonest advice. Note that wheel bearings can go bad at any mileage due to damage, but from pure wear they should definitely last longer than 80k.

On the tires it also depends on why they came to that conclusion. Tread depth isn't the only thing to watch out for, uneven wear or cracks from UV damage/age could also influence that advice. But absent of rationale for the recommendation it is rather meaningless.
 

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we might need the name of this dealership - someone in the future may search here for places to avoid
 

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How many miles on it?

I never had the idle speed sensor fail on the Subaru but with our VW the sensor once warmed up started to fail and the car would start to go into a limp mode at first it was an hour into a drive. Then it got shorter and shorter. It also would stall and not restart till it had cooled down but that was at the point you could only go about 20-30 minutes. I had a similar experience with my toyota same deal idle speed sensor was failing and caused the car to go jnto
Limp mode.

If your at more than 120,000 and never did tge sparkplugs that could be a contributing factor. I would also assume the timing belt job was never done at 105,000 if the plugs were never done. Which case have both done asap!
 

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Discussion Starter #9
Car is at 80-81k at the moment. I actually plan on acquiring the parts for the timing belt job in advance. Is there a sticky or a well referenced thread on here in regards to it?

Oh no the tires are not cracked or show uneven wear. There is a vibration at about 65mph, but this appears to be a tire balance issue, car is smooth sailing otherwise.

Where is the idle speed sensor located? I'll clean the MAF for sure and see what happens after that.

Thanks for the advise OBDad! I'll check out those resources.

Honestly Subaru's are pretty foreign to me. I've owned GMs all my life, I suppose the closest thing I've had happen to me like this was the ICM on my LT1 back in the day. Does the Subaru have an ignition control module?
 

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Ignition stuff rarely ever fails on the Subarus. I would suspect cvt fluid level before the ignition coils.

One thing be very careful with sensors that scew into the block. Lots of people have cracked the threaded area cranking them tight. They dont need much to be tight.
 

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No idea on the idle speed sensor. Never had to mess with it on the subarus. But your description of whats going on once warmed up is very similar to my VW and Toyotaexperience
 

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Discussion Starter #12
You know what's hilarious about this situation though? This is the kind of thing where you wish the check engine light would come on during the occurrence and actually mean something. Do you think the check engine light comes on during this? No, of course not haha. So I probably won't get around to looking at the MAF until Tuesday. Ah well, hoping my wife doesn't crash my Sierra in the mean time.
 

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We've got a 2011 2.5 Outback with 50k on it, which had similar issues (ie- low power, poor mpg, rough-ish idle, etc..). I've recently replaced the fuel pump assembly which has seemingly cured the car of it's issues. Good luck with it.
Regards
 

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Discussion Starter #14
I did pull a spark plug yesterday, the threads looked pretty rusty, I'm guessing they have not been out of the car since the factory put them in. They are NGK iridiums, SIFR6A-11, is this also the recommended replacement plug? $40 for plugs hurts haha.

Not to get completely off track, but based on the plugs appearing to not having ever been changed, yeah I will be changing the front and rear differential fluid, doing the drain and fill on the CVT based on what I read in that sticky, and probably the cabin air filter has never been done. When I get a new air filter, does it include both sides? I pulled the air box apart yesterday and saw that it looks like two filters. Thanks in advance!
 

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Engine air filter has two elements (2.5 PZEV models)

One element (the familiar paper one) should be changed regularly.

The other is a carbon element for trapping evaporated gasoline, and does not normally need replacement.
 

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Stick with the ngk plugs. Subarus are famous for having issues with everything but ngk. No joke. I would also assume the timing belt job has never been done either.
 

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Discussion Starter #17
Well I know the timing belt is due at 105k, car is at 81k. Do they have to be the SIFR6A-11 NGK plugs though? Or is the an accepted alternative part number? I see them on Amazon, at almost $14 each or $43 for a pack of 4.

Thanks for the info rasterman, I'll ignore that second filter for now then.

Does this vehicle have an external fuel filter or no? I know most vehicles went to an in tank filter quite a few years back...
 

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Bother, they need it.....

Fuel filter dont bother. Unless your buying fuel off unmarked trucks south of the border and pre filtering it through a T-shirt?
At 50k, that little sock of a strainer/filter at the base of the pump was completely clogged with debris and we're not "south of the border". It was killing the mpg, plugs, and detonation quality. We could have done ours at 30 or 40k. That f-pump was some of the better $300 we have spent on the car and not terribly difficult to change out. Better then being stuck in the woods in the PNW/Canada.
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Well I know the timing belt is due at 105k, car is at 81k. Do they have to be the SIFR6A-11 NGK plugs though? Or is the an accepted alternative part number? I see them on Amazon, at almost $14 each or $43 for a pack of 4.

Thanks for the info rasterman, I'll ignore that second filter for now then.

Does this vehicle have an external fuel filter or no? I know most vehicles went to an in tank filter quite a few years back...

You can use the BKR6EGP. They're a lot cheaper but they also don't last as long, so be ready for that in a year or two.
 
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