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2015 Forester XT Premium CVT
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142 Posts
It will take a bit after pulling the battery for the trims and waste gate settings to adjust. Mine was perfect after the 2nd tank or so.


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Thanks. I'll wait a few tanks to update. Also time for an oil change so I'll let Subaru do this one and ask if my ECU has the most recent software fix.
 

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2015 XT Touring
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186 Posts
I'm convinced that this is a tuning/ECU problem and not an issue with the hose clamps as others have speculated. I was going to do the DANOZ turbo clamp fix as I figured at 40k miles and the summer months approaching and things getting hot, it was an issue related to wear or something becoming lose. I was a little skeptical at first as I had already replaced many of these clamps when I did my charge pipe and turbo inlet hose upgrades. But I decided to go through the car and check everything anyway. All hoses were tight, even the ones I hadn't replaced were tight. Fast forward a week later and I get my accessport. Installed the cobb stage 1 tune and all these issues completely went away. Doubt it is a coincidence, haven't had a problem in the past 4 days. Even on my 4 hr road trip yesterday I had zero issues. Anyone here have a tune and are still having problems?
 

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2015 Forester 2.0XT H-CVT
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359 Posts
Thanks for that input Clean15'. I was out in desert heat yesterday. Car showed outside Temp at 119, I was running the A/C with 5 people in the car going slightly uphill. Oil temp was higher than usual at 230 F. I had some surging happening. But nothing too major. I went from sea level to 6000 ft in elevation. During that climb there was a ticking sound that lasted about 1 second, felt like a slight loss of power. This is the 3rd time I observed this clicking sound, seems to happen when ever I climb in elevation. Coincidetally, I have a giant 64 ounce metal flask, whenever I go up in elevation it makes a loud POP and when I drive down the mountains it pop and implodes.

After a night of camping up in the mountains there were no surging issues on the 150 mile drive back home.

It sounds like this surging is really finicky. Is there an explanation for why our cars surge? Is the ECU protecting the engine from damage be retarding it?

I would feel much more at ease knowing that my car surges to protect the engine from damage. If our foresters are surging because they are about to fail, then I'm going to be really really worried.

Anyone out here have surging issues before catastrophic failure?


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2014 Forester
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58 Posts
It really does sound finicky. The clamps worked for me, day and night difference. Was thinking about selling the car because it drove so odd in the Texas heat with family onboard.

Seems like there could be underlying issues for other drivers out there though.

Im wondering if it is a carbon build up thing or fuel quality. I noticed the car drive even better after about 800 miles on our road trip, oil temps were at 212 almost non stop. I wonder if that helped burn some junk off.

Maybe give it a good spirited drive for a few hundred miles.

I really hope everyone gets their issues fixed because this car is great when it runs fine, when mine was not running good I almost felt as though my old 2.5i was a better drive.


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2016 XT
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283 Posts
Discussion Starter · #325 ·
Just an update to my problem,

It seems that Subaru OZ has finally gotten the ECM update and I have just got back from having it installed, the paper work says "ECM update for spark knock at high intake temps which may cause surging" or as the advisor wrote "serging" :lol:

Anywayz time will tell if its fixed now as it is now winter here with a cold 25 C here today :wink2: I shall be using 95 RON fuel from now on until I'm happy that the problems are fixed.

I was having the surging problem when using 95 RON fuel (but not with 98) and some very random pre-ignition events around the same rpm's on both grades.
 

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2015 Forester XT
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16 Posts
I was on a long road trip over the weekend and I could recreate the surging at a specific acceleration. These are the factors that it happened consistently.

Accel 30-40% (as measured on dash gauge)
RPM 2000-2200
Boost ~10psi

Speed was about 60mph on a slightly uphill grade. I was able to recreate the surging if I held these variables consistent. If I accelerated past 2500RPM the issue went away. I had no trouble climbing hills at higher boost and RPM. The surging repeatibly occurred when these were all met.

It almost felt like a fuel delivery issue, or like it was trying to select the correct "gear" in the transmission.

Any thoughts?

Also doesn't seem to happen while using cruise control at any speed...

As a note: my breeze liner clamps need a turn of tightening every 1000 miles. I feel like I got them plenty tight on installation. Don't know what's going on.
 

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2015 Forester 2.0XT H-CVT
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359 Posts
I was running a KNN drop in box filter. My FXT was having weird surging in 80 degree F weather so I went to he dealership and changed it out with a OEM drop in filter.

I inspected the KNN filter and noticed it was a little dirty. It was black in the shape of a circle and that circle only covered about 1/3 of the actual filter. The circle was off centered closer to one of the corners. It's hard to tell how dirty it was since the KNN filter is a deep dark burgundy color.

So immediately after the OEM filter install, I still had surging, but it felt shorter and mitigated. With the KNN filter it seems the FXT would surge about 3 times in quick succession. Immediately after the OEM filter install it would surge 1 time. After a day, it was gone.

By the way. I purchased my 2015 FXT used with 10K miles from CarMax. Carmax puts the cheapest parts on the cars they sell.

The first thing I did after purchasing the car was change out the oil and engine air filter, since they're cheap aftermarket brands.


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2011 XT Touring 4EAT
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12,185 Posts
I'm convinced that this is a tuning/ECU problem and not an issue with the hose clamps as others have speculated. ................................. Anyone here have a tune and are still having problems?
it def, 100% is. many many people have had it completely go away with the Cobb OTS tune. some had it get better, but still had slight instances here and there...but again, because its an Off The Shelf tune, just like the oem subaru one. all cars are slight different, and in different areas/locations.

no one thats had a tuner tune their SJ, has this problem. no one.
glad yours is better man!
 

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2011 XT Touring 4EAT
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12,185 Posts
people in extreme environments/instances (outside temps above 100, humid, hauling stuff, etc etc) are going to experiences instances of the car struggling for brief instances. youre in an extreme settings, and pushing the car (whether you think you are or not). this is a great example, imo:
Car showed outside Temp at 119, I was running the A/C with 5 people in the car going slightly uphill.
my point, like in my previous post, # 329...is in normal situations. the many people who have been cruising down the road, temps in the 70s and 80s, and just looking to use the go pedal. like @Whitetop just mentioned.
Speed was about 60mph on a slightly uphill grade. I was able to recreate the surging if I held these variables consistent. If I accelerated past 2500RPM the issue went away. I had no trouble climbing hills at higher boost and RPM. The surging repeatibly occurred when these were all met.

It almost felt like a fuel delivery issue, or like it was trying to select the correct "gear" in the transmission.

Any thoughts?
its a pre detonation issue. high cylinder temps. "knock". happening in a scenario where the engine has essentially the biggest load on it. and your ecu backing off, so itll stop knocking. so it doesnt go kaboom!
in other words...your car is trying to get up and go...but says,"waaaait, whats that? waaait, whats that?

-I will take note of the DAM and fine knock numbers after my drive tomorrow. I haven't noticed anything crazy, but you may know otherwise. The log I sent to Cobb was WOT, and not an instance of this surging. I may try to log the issue while the surging is occurring.
^^did you ever get a chance to do/check this out man? id be interested to see what the log looks like. WOT one from 3k up towards redline. then another one in the surging scenario. log DAM, feedback knock correction, fine knock learn, af learning 1 and boost. to see.
also...can you get 93 oct, in case youre not using it currently? is it worse if you unmarry the AP, then drive for a couple days?
 

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2015 Forester 2.0XT H-CVT
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359 Posts
its a pre detonation issue. high cylinder temps. "knock". happening in a scenario where the engine has essentially the biggest load on it. and your ecu backing off, so itll stop knocking. so it doesnt go kaboom!
in other words...your car is trying to get up and go...but says,"waaaait, whats that? waaait, whats that?

That's what I thought it might be. In a previous post I inquired about this. So, this surging is to protect the engine. We should not be too worried. So we need to make sure we all use premium fuel, OEM air filters (unless you get a protune), anything to control engine knock.



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2015 XT Touring CVT
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45 Posts
It's been a long time since I last posted on the forums at all, however I had the most significant issue to date with my 15 XT this weekend.



Long story short I was driving in/around Lancaster and Palmdale, CA this weekend. Air temps 110-115 F and my oil temp got 230 F. I've had intermittent surging issues (described in previous posts) like most have suffered however these 3 days were the worst. I'm an engineer and not one for the dramatic, but my car was dangerously un-drivable throughout my weekend. In all modes (I, S, and S#) both in automatic and paddle shift modes, the car would buck/shift/shutter and/or fall flat upon acceleration. I fought and fought the car through all 3 modes just to get from point A to point B (kids softball tournament) and couldn't get it to stop surging as I'd done in previous occasions. No kidding in automatic S mode going about 40ish mph, I floored it (yes I know I should roll on the accelerator with the CVT) and the acceleration % "meter" went to 100% and the car did NOTHING!



Low and behold I came back to San Diego on Sunday and had a letter waiting in our mailbox from SOA telling me that my CVT powertrain coverage had been extended to 10 years/100K miles and the offer of a free (although not required) inspection of the CVT. I've already made an appointment at the dealer for Wednesday.



I've always felt the issues we've experienced are horrible combo of crappy ECU tuning/CVT design/lack of cooling for USDM CVT but at this point I'm about to give up on this car and I'm on my 3rd Subaru.



Without searching every nook and cranny of the forums for peoples experiences over the last year, does anybody have any suggestions for how I should handle my dealership appointment in 2 days?
 

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2011 XT Touring 4EAT
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12,185 Posts
So, this surging is to protect the engine.
no (ish...). its the by product/result of the ecu stepping in to help protect the engine.
We should not be too worried.
if i had a car under warranty, with no/minimal desire to rip into it and make performance modifications (like i just bought the car to drive it as is..)...i wouldnt be worried at all. let the dealer figure out any thing/issues that may arise from it. aint my problem.
if i had a car under warranty, but i didnt really care about that, as i intended to rip into it anyway and make performance modifications...i would be very worried = if i didnt have a way to monitor the knock, and associated parameters...with a device like a Cobb Accessport...and still somewhat worried even if i did have a device like that...and saw the knock happening.
So we need to make sure we all use premium fuel, OEM air filters (unless you get a protune), anything to control engine knock.
very smart idea(s).




...and all this is just my opinion. because i havent seen info to sway me into thinking other wise. but have seen info to support my thoughts.
 

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2014 Forestor XT
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1 Posts
Just an update to my problem,

It seems that Subaru OZ has finally gotten the ECM update and I have just got back from having it installed, the paper work says "ECM update for spark knock at high intake temps which may cause surging" or as the advisor wrote "serging" :lol:

Anywayz time will tell if its fixed now as it is now winter here with a cold 25 C here today :wink2: I shall be using 95 RON fuel from now on until I'm happy that the problems are fixed.

I was having the surging problem when using 95 RON fuel (but not with 98) and some very random pre-ignition events around the same rpm's on both grades.
Never had that surge(& lag) problem - until a ECU "refreshed". It took the Motorimage (local Subie distro) nearly 3 months before they reflashed the new ECU update. My experience is: if it is ain't broken, don't flash anything. But once broken, keep stalking them till it is fixed.

Now I'm happy that the problems are fixed...except now my head unit bluetooth kept shaking off my iphone connection - in the middle of a call...:frown2:
 

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2016 XT
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283 Posts
Discussion Starter · #335 ·
Never had that surge(& lag) problem - until a ECU "refreshed". It took the Motorimage (local Subie distro) nearly 3 months before they reflashed the new ECU update. My experience is: if it is ain't broken, don't flash anything. But once broken, keep stalking them till it is fixed.

Now I'm happy that the problems are fixed...except now my head unit bluetooth kept shaking off my iphone connection - in the middle of a call...:frown2:
Yeah you probably had the update/recall for pre-ignition in 2015 iirc, and that's when most started to notice the surging and I suspect my 2016 MY had the same software.

What fuel octane do you use?
 

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2015 Forester XT
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2 Posts
My Forester XT 2015 with over 16,000 miles on it is having mild surging as well, at low acceleration, approximately below 25% level, and speeds somewhere below 45 mph. This is especially felt in medium traffic where traffic slows down a bit, then starts moving. Don't know the cause, but the feels as if there was and a few second accidental down shift. This behavior is most felt at Intelligent mode and S-sports mode. Not so much on sports # mode, but I rarely drive in sports #, only on rare occasion, so will need to verify that S# again.

Yesterday it was around 70-75 degrees degrees outside and this behavior was happening after 15 minutes of driving or so, when traffic started to slow down on a highway. The engine temperature was above 180 degrees Fahrenheit, towards 200 degree mark. I started noticing this behavior this summer, surging appears to get stronger, while the ambient temperature is no where near 100 degrees others reported with this condition.

Oil regularly changed at shorter intervals than standard recommended. Using top-tier fuel / premium.
 

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2016 Forester
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13 Posts
Undecided about pursuing CVT class action

Just minutes ago, Facebook flashed an ad up about a Class Action Lawsuit pertaining to CVT problems in '14-'18 Foresters, which piqued my interest. Googling turned up this forum thread and another like it, in which owners share (and refute!) each other's experiences.

In my case, driving a cherished 2014 Forester 2.5L with only 29K on the odometer, using regular unleaded (83) gas from Costco, I *do* notice shuddering at light acceleration. Though I haven't logged the issue closely, I can say it normally occurs when proceeding from a stop, always at very low speed and not lasting more than a few seconds, happening within a few minutes of startup, mostly on warm days with dry weather while the air conditioner is running. But, then again, those conditions describe 99% of all my driving, as I commute almost exclusively within a 3-mile radius of a hot southern city and drive like a granny.

Service-wise, I change my oil every 5,000 miles using synthetic Mobil 0W-20 per manual, and have my wheels aligned at Firestone (for free, using my $200 lifetime Alignment plan) every 6,000 miles, keep the engine clean and change air filters regularly whether they need it or not. Still on factory spark plugs and timing belt, because they are immaculate.

I also got a form letter from SOA last month explaining that the Warranty would be extended until 2018 for the CVT, which was a nice gesture, but as stated I have not had any overt problems or drivetrain service performed to date, and no Recall or TSB has been issued that I can find.

If it helps, I'll do my best to document the situation, but hasten to add that this engine/transmission behavior does NOT bother me much; my passengers (rarely more than 1 in the car, so carrying <500 lbs. total cargo+humans most of the time) occasionally will comment. When they do, I attribute the "jutter" or "lurching" to the CVT, because it's the only mechanical process that makes sense to me and matches what reviewers warned about before I bought my vehicle.

Whether I would ever join a class action lawsuit over this minor issue is up for debate, as I have little faith that a manufacturer or dealership can solve such an intrinsic or nuanced "malfunction" (to me, that's an unfair word if I expect the behavior from day one), and my expectations are low. I love my car as-is. If it happened more often or affected my enjoyment, I might pursue the matter more vigorously, so can understand why others are motivated in that direction.

Thanks to everyone for sharing your viewpoints.
 

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2015 Forester 2.0XT H-CVT
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I get surging every now and then. Like everyone said, its “mild” so it’s manageable. I wish it never happened. Hopefully there could be better cvt reprogramming in form of a recall?

I tried telling my dealership about the available update but they won’t update the programming unless they can reproduce the issue.


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'21 ISM Crosstrek Limited
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I get surging every now and then. Like everyone said, its “mild” so it’s manageable. I wish it never happened. Hopefully there could be better cvt reprogramming in form of a recall?

I tried telling my dealership about the available update but they won’t update the programming unless they can reproduce the issue.


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It's not your CVT.

It's not the ECU's programming... it's doing its job and your symptoms are the result.

It's your gasoline.
 

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2015 Forester 2.0XT H-CVT
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Most of my issues with surging have been in hot weather while going up steel inclines while having lots of passenger weight in the car 1000 lbs.

The car will perform admirably, and then the surging symptoms pop up and will persist for a few days.

One thing I have learned, is that switching my Forester XT to manual mode (tapping the stick to the left while in drive) will completely make the surging go away. I have accepted that this is the only safe way to go up a steep hill without having to deal with surging or a loss of power.


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