Subaru Outback Forums banner

2016 OB "surge/stumble/lag"

31K views 54 replies 31 participants last post by  sb001 
#1 ·
New member, I've been lurking off and on for a few years. I've owned nine Subarus, currently own a 2016 2.5i Limited Outback and 2016 Forester 2.5i Premium.

I've read the few threads/posts on here regarding "surging/stumbling." My 2016 OB surges/stumbles EVERY time when applying "part-throttle acceleration" from a stop. What I mean is, I push the accelerator a small amount and the car reacts as if I'm accelerating in 2nd or 3rd gear from a stop in my 2011 WRX. I keep the accelerator at the exact same position, not giving any more or less force, and it sloooooowly accelerates, then, once it hits a certain speed, "jumps" (surges) forward, like I just passed a rich spot in a carbureted vehicle or made it through some turbo lag. Sometimes this surging is accompanied by various "stumbling," with the CVT "hunting" around a bit before it "bites" and accelerates smoothly. It does this whether the motor/transmission is cold or hot, no matter the outside temp, road conditions, etc. This only happens when I accelerate at a slow-to-moderate pace, not at 1/2 to full throttle starts, which are normal.

If I shift manually using the paddle shifters, this issue doesn't happen. I'm pretty much convinced this is a CVT programming issue. My background: I recently worked at a major automotive manufacturer's Torrance, California HQ as Senior Technical Editor for Owner's and Service Manuals for almost a decade. When I say I'm convinced it's a CVT issue, let's just say I'm pretty convinced.

I'm wondering how to get Subaru to do something about this. Having worked for a major automotive manufacturer, I know how difficult it is for them to address an issue they'd rather not acknowledge. So, my questions for those on here are: 1) Has anyone experienced this issue?; 2) If so, has anyone had luck getting it "fixed," whether at the dealer level or with an escalation to corporate?; 3) Is this an issue dealers are aware of and have a fix for (TSB, technical service bulletin)?

Again, mainly I'm looking for some background on the issue before I approach Subaru.

Other than this "surging/stumbling" issue, I love the car. And yet, every time I drive my 2016 Forester, also with 2.5 and CVT, I'm reminded how sub-par the CVT programming is in the OB. The Forester's power train behaves perfectly.

Thanks for any feedback.

 
See less See more
#2 ·
could you experience this in ANY 2016 Outback? That is, do you feel this programming problem presents across the entire fleet? Have you tried disconnecting the battery to reset the TCU? maybe it has 'learned' some odd performance?

I'd think a laptop or similar arrangement could record the necessary parameters while you recreate the problem - perhaps a SOA regional rep could arrange such a test. With you driving, throttle position and other parameters could be logged and examined - once a tech saw what you were doing with the throttle, anyone should be able to duplicate the issue.

It may very well be difficult to get SOA interested in this - particularly if it isn't reasonably interpreted as a safety problem. But SSM or similar logging while you duplicate the issue is definitely do-able. You might be able to do it yourself with RomRaider or Torque or similar - present them with the logs.....?
 
#3 ·
Thank you for your reply and suggestions. I have not driven other 2016 OB models at this time, but will be sure to do so when I take mine in. I think if this issue was fleet-wide, I would have read multiple threads/complaints, but I've only seen a few that were somewhat similar. I was hoping to "stumble" on someone who had the same issue and had it fixed so I could present that information to the dealer versus going through the typical "Service Technician could not replicate" back-and-forth.

I have not reset the TCU; some quick reading indicates various systems need to be reset after disconnecting the battery. Is it simply a ground disconnect (for X minutes?) that does it? I did find the list of reset items PDF on the forum.
 
#4 ·
... I'm looking for some background on the issue before I approach Subaru.
The phenomenon has been discussed several times previously on this forum. What you are experiencing is most likely an artifact of torque converter lockup clutch engagement, which requires simultaneous compensating adjustment to the CVT ratio. The situation should improve somewhat over the first few thousand miles, as the TC clutch surfaces wear in and the CVT controller "learns" the optimum behavior.
 
#5 ·
I keep the accelerator at the exact same position, not giving any more or less force, and it sloooooowly accelerates, then, once it hits a certain speed, "jumps" (surges) forward, like I just passed a rich spot in a carbureted vehicle or made it through some turbo lag. Sometimes this surging is accompanied by various "stumbling," with the CVT "hunting" around a bit before it "bites" and accelerates smoothly. It does this whether the motor/transmission is cold or hot, no matter the outside temp, road conditions, etc. This only happens when I accelerate at a slow-to-moderate pace, not at 1/2 to full throttle starts, which are normal.
I've played around with this approach myself, as part of trying to educate myself about what to expect from the CVT, and I can't say I get the results you're describing here.

As you say, when accelerating with some authority the transmission shifts "normally", which is to say it steps through the 6 programmed shift points reliably and repeatably. The more throttle is applied the "higher" the shift points are relative to engine speed. I'm supposing this is the way things are programmed to work.

However, when accelerating very gently from a standstill, and then very carefully holding the accelerator in a fixed position with the engine rpm around 2000 or so, the car will accelerate gently (almost always after noticeably "shifting" into "second gear"), with the engine speed remaining constant as the road speed smoothly increases.
In other words, the CVT will perform as if the programmed shift points don't exist at all (which would be lovely, but that's a different discussion).

Getting this effect is tricky—a little too much throttle and the shift points become noticeable again, while not enough will fail to accelerate the vehicle continuously—but I can't say as I've experienced any real hesitation or "hunting" such as you describe unless I play with the throttle position to deliberately try and produce that kind of "confusion."
 
#6 ·
@ammcinnis:
I understand the explanation, but am wondering why this behavior is experienced on the OB, but not my previous 2012 Legacy w/CVT or my current 2016 Forester w/CVT. I've had the the OB for four months now (just a bit over 2,000 mi on it), and waited for what I thought was a reasonable amount of time before bringing it up. Is this something that is vehicle-specific? Some vehicles experience this but not others? If so, why? Manufacturing tolerances?

@gunnison:
Interestingly, I don't recall my 2012 Legacy having "shift points" programmed. It exhibited the typical CVT "go to optimal position and stay there" behavior. Which I didn't really mind -- I understand many dislike the "droning" sound that brings with it. Why program "shift points" in -- doesn't that defeat the purpose of a CVT?
 
#8 ·
I believe our 2016 3.6R is experiencing the same problem. Ours was nice and smooth for the first 3200 miles, and just started doing this in the last ~100 miles. The 'surging' seems to occur after the TC has locked up. It doesn't happen all the time, but maybe 25% of the time. I've searched the forums too, and the only thing I found that sounded like this was a comment made in a converter lock-up thread (i think), and the poster stated that the issue was taken care of with a reflash.

Pat
 
#10 ·
Thanks for all the feedback. I certainly find it objectionable, seeing as none of the other vehicles I've had with CVTs exhibited this issue ("trait," to be kind). They were noisy, yes, but never any lurching/surging/hunting/lagging. (If you're curious, a Nissan, a Honda, and the Legacy and Forester.)

I do get that driver "behavior" may make the issue more prevalent, but it's disappointing to hop in my Forester, drive exactly the same, and enjoy a smooth, consistent drive every time without this issue. It makes the OB drive train feel underdeveloped. Mind you, if you mash the accelerator every time from a stop you'd never know about this. But if that's the way I wanted to drive I'd still have my WRX.

So would the dealer "reflash" do anything? Or is that just a panacea for the customer's peace of mind?

I hope others experiencing this "trait" will post their experience in this thread.
 
#13 ·
The first thing I would try, as @1 Lucky Texan suggested, is to remove the ground wire on the battery for 30 seconds and drive it for a few days afterwards. If that doesn't "fix" it, then I would test drive another Outback and see if it does what you are describing too. If not, then I would drop it off with a dealer and take the service writer/tech on a test drive, with you driving, and show him/her the problem. Sometimes a tech can't replicate the issue without knowing exactly what it is supposed to do. That's really the only 3 routes you can take at this point.

(2014, 2015, 2016) Subaru Forester 2.5L CVT AUTOMATIC TRANSMISSION ASSEMBLY . TR580GHZAB. Part # 31000AJ330

(2015, 2016) Subaru Outback 2.5L CVT AUTOMATIC TRANSMISSION ASSEMBLY . TR580SHACA. Part # 31000AJ610

FWIW, the part numbers are different. But it appears as if they are both the TR-580, so that leads me to believe they mostly the same. L
 
#12 ·
@bmw111
I'm curious if your OB's drive train exhibits any lack of smoothness when the throttle response is under control of the Cruise Control. (Not ACC, which we don't have, but just regular CC)
Our OB does not. When the car is in CC the transmission will adjust, up or down, to accommodate different load conditions imposed by hills or whatever as smooth as silk, without any discernible "shift points" at all. And this on freeways across the Western high desert and even over mountain passes, where at a constant 70 mph the engine speed might easily vary from around 2000 all the way up to 4500 on the steepest sections.

This smoothness is evident even if the road speed drops down to a relative crawl, like when CC has been cancelled manually or by braking for a traffic logjam, say.
Hit "resume" and the car will accelerate very smoothly indeed all the way back up to whatever the original highway speed setting was.

I do wish the "shift points" were not programmed in, except for paddle shifter operations, but again that's a different discussion.

In order to get anything like the symptoms you describe, I'd have to deliberately drive in such a way as to go looking for them, and even then I'd describe them as mild.
My habitual driving habits for any vehicle are the same as my habits with the operation of any kind of power tool (and a vehicle is exactly a power tool), which is to adapt my operating style to produce maximum smoothness of operation for that tool.
Once I "got the hang" of this model Outback's characteristics, it's been very smooth performer.
 
#18 ·
Pegasus,

Our 2016 3.6R just started exhibiting this issue, so that doesn't seem to be the differentiator. It was perfectly smooth for the first 3000 miles or so, and out of the blue started doing this.

Pat
Understood. My 3.6 has almost 10,000 miles on it and as I said, it does not suffer from this. So while the engine may not be a differentiator, this issue is not affecting all Outbacks.


I'm in Europe this month, so I won't be driving my 3.6 for another few weeks. And that's sad.
 
#16 ·
@gunnison: My 2015 3.6R has will "surge" in ACC mode at times, underlay, going up hills, etc. The Cruise is not as good as it was on my 2012 Impreza Outback Sport. Meaning, with gears (AT on the Impreza) - the CC would hold speed "very well", best of all cars I ever driven. With the CVT here in Pittsburgh, there are some hills where, as the grade increases a bit more rapidly, the load gets higher, and it will shift down to rev up to > 2K (normal driving is ~ 1650rpm). Once it reaches speed, it will settle down OK. . .
Same thing happens when speed is low (say 50, CC set to 60) and the tractor-trailer in front moves over, the ACC will "stomp" on the gas to get back up to speed. Over time, you get use to it, just some things to be aware of (36K miles on mine)
Otherwise, as @ Pegasus says, I don't have any issues, with takeoff, and I'm a "light foot". I don't hit "Shift points" until the tac is well over 4K (yea, been there a couple for times). Otherwise, if I say < 4K, I can hold acceleration well.
 
#17 ·
I have not experienced any of this lag or stumbling @ 5k miles on my 16. As others mention, try a soft reset and have the dealer check for any updates.

I have changed my driving habbits a bit to enjoy get the best out of the CVT. Around 15 - 25 mph the way the cvt reacts is a bit "jumpy" when on and off the throttle. I find being easy on the throttle initially and then accelerating produces better results. Also, don't baby the car all the time. You need to open her up a little here and there.
 
#21 ·
I notice this'surge' on my 2.5i now that I have the AC engaged all the time. As I brake at aspeed below 15mph to a stop, the engine accelerate against the force I apply to the brake pedal. This happens whether the engine is up to temperature or not. And it also happens when Im backing out of the garage in the morning. It does not surge at stop.

We develop a habit of breaking that works with what we are trying to do. (Those who break with their left foot need to develop another habit.) My habit is to allow the engine to assist in slowing the car by not over-accelerating and letting off the acceleration pedal in anticipation of slowing down. This allows me to use a soften force on the brake pedal for the final stop. With this surge, I apply more force to the brake pedal at a point below 15mph.

Is this surge worth a visit to the dealership service? Does removing the battery ground for a period really re-set some transmission sensor? Do I develop another habit?
 
#24 ·
At about 15mph the torque converter unlocks. This greatly reduces the engine braking, and it feels like a surge under light braking. Perfectly normal, either get used to it or start doing panic stops everywhere.
 
#22 ·
Cars do have a learning module that records certain driving habits. I don't believe this is reset in a "soft" reset. On my Lexus vehicles it did not. I would try the soft reset and see if she act any different as well as see if there is a software update for your vehicle via the dealer.

I don't experience a surge as you describe but it could be the cvt "down shifting" or engine braking. Also keep in mind the rpm's will be higher when the engine is warming. This will require more brake force to stop the vehicle.
 
#23 ·
I believe all 5th Gen 2.5i Outbacks have that surge-stumble on launches. I do notice it with mine.

However, I was able to retrain my right foot to avoid it. Now I normally launch from a stop by slowly rolling onto the throttle gradually pressing it further the faster I go. I used to get going by pressing the throttle down ~0.75'' to get the car going then give more or less as needed and the car would lurch off the line. It feels like slowly rolling onto the throttle gives the torque convert more time to lock up which makes it smoother, similar to manual when you roll-off the clutch compared to popping it. I find it's easiest to roll onto the throttle for slow starts but it is possible to get going quickly with enough practice.
 
#25 ·
I have a similar problem. When accelerating from a full stop or slowing down for vehicle in front the Outback feels like it's not getting any gas. It's a problem because if you slow down to say cross over a 4 lane road to get into a parking lot I accelerate but the car doesn't respond for a second or 2 and if your timing yourself to avoid oncoming traffic (which you would make with no problem if car accelerated) makes you heart skip a beat. Brought it to dealer and nothing shows up on computer and of course couldn't get it to do it when tech took it for test.
 
#29 ·
2016 Legacy 2.5 Light acceleration surge

Ladies/Gents,

I have the described issue too with my '16 Legacy 2.5. When I do accelerate lightly(which is most of the time), it is almost impossible to have smooth acceleration. What exactly happens is: I press the gas pedal to about 15 or 20% per my info display(just a light press), and I try keep it constant, but the car initially surges, then slows a bit and then at 15 - 25 mph, I feel a second surge. These surges are not happening when I accelerate harder or at higher speeds(above 40mph). The issue is not too bad, the car is drivable, but it is definitely annoying.
I've had an Altima CVT in the past and I recently tried the latest Altima, just to make sure it is not "me", and it isn't me.
I also think it is a software issue, either with TCU or throttle positioning sensor, since with the adaptive CC On, when the car stops and then starts accelerating on its own, I can barely feel the surges.
So, I am going to the dealer next week. I was thinking to disconnect the battery for a while to eventually make the TCU learn again and see if there is any change, but I have to visit the dealer for a recall, so I will see what they have to say about the acceleration.
 
#31 ·
There is a sensitive spot around 15 to 25 mph with the cvt. It is particularly notable in traffic. Try rolling on and off the throttle gently. It takes some getting used to as the cvt is not quite as smooth as some traditional transmissions. At least compared to my last 2 Lexus vehicles. You may need to adjust your driving habits a bit to minimize this "jerkiness". If you are truly experience your engine stumbling then something else is wrong.
 
#32 ·
It sounds like most everyone who has taken their vehicle in has been told it is within spec for the transmission to behave like it does, just annoying.
At this point is there anyone on the forum that's been successful in having a "re-flash", replaced torque converter, or any other actual dealer fix for this common transmission quirk?
Thanks!
 
#33 ·
OB 2016 lurching at slow speeds

I am having the exact same lurching problem in my 2016 OB. Just purchased it and it started this behavior at around 4500 miles. Happens at slow speed when I am just starting out and when I slow down almost to a stop. This lurching is very annoying and has nothing to do with "how I drive".

I rent tons of cars while I travel and have owned a bunch of Subaru's. Never had this before...

I plan to go to my Subaru dealer this week to see if they can trouble shoot it.
 
#34 ·
Just an update. I finally took my '16 OB in for its first service (yeah, I don't have a long commute). Took a test drive with the technician and while it did surge a bit, he didn't notice it. He later drove it after the oil change and said he didn't notice it at that time, either. Of course, this is exactly what I expected, since it's something that is tied with the percentage of throttle applied and what a driver expects from years of applying said throttle percentage to various other powertrains and NOT having a surge/stumble/lag.

Still like the car, but honestly, if I hadn't leased this one, I'd just turn around and trade it back to the dealer for either a 3.6R OB or maybe another Forester -- which has the same powertrain as the '16 OB but never exhibits this issue.

FYI, I'm the OP in this thread. I started this thread when I had around 2,000 miles on the OB and now have around 7,500. The issue still exists, but is either a tiny bit less obvious or I've just convinced myself to ignore it. If anybody has had success getting this resolved, we'd like to hear about it.
 
#35 ·
My two cents: I've come to the conclusion that each OB has its own personality, particularly when it comes to the throttle. As part of my shopping process, I have driven seven 2015/2016 OBs over the last 6 months, either new or used, 3.6 or 2.5. One thing that surprised me is how different they could feel, and how these differences were not predictable. The first OB I tried shocked me: I almost had a whiplash. Three others had a noticeably sensitive throttle from a stop (two 2.5 and one 3.6), but not as drastic. Another 3.6 felt weirdly slow, as if it would take its sweet time to get moving, its power only showing off once above 30-40 mph. The 2015 2.5 I ended up buying has a very normal throttle, quite similar to the one on my old CR-V and other cars I've driven. The "surge" didn't seem to be correlated to the mileage.

Anyway. Maybe I'm just crazy.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top