('14+) 2.5i Prem CVT- gentle bucking at light acceleration (Merged Thread) - Subaru Forester Owners Forum
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post #1 of 209 (permalink) Old 06-12-2013, 07:45 PM Thread Starter
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2.5i Prem CVT- gentle bucking at light acceleration (Merged Thread)

I've owned a Limited (my first Subaru) since May 1st and love it. I've never had or driven a vehicle with a CVT and am looking for some feedback. When I accelerate from a dead stop it tends to be "jumpy" as it comes up to speed, you can feel small lurches and it is definitely not smooth, and this is no matter how light I am on the gas pedal. Once up to speed it cruises around just fine. Is this a normal behavior for a CVT or does this sound like a possible problem? It seems to be worse when the engine is cold and lessens when warmed up but it is still there. Thanks.


Last edited by broken; 06-15-2013 at 08:14 PM.
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post #2 of 209 (permalink) Old 06-13-2013, 05:18 PM
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I heard some outback owners complaining about this when the outback first came out. I would report it to the dealership as it is most likely a TCU (transmission control unit) problem. If something is wrong the the TCU (probably just the "tuning" of the transmission), Subaru will make an updated flash and it takes a few minutes to flash the computer to the new map.



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post #3 of 209 (permalink) Old 06-13-2013, 05:51 PM
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I have '14 N/A with the CVT and never experienced what you described.

I would take it in and have the service guys take a look at it like Loscaldazar said.

Plus there is a little getting used to a CVT if you never driven one before. Took me about a week to get used to it.
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post #4 of 209 (permalink) Old 06-14-2013, 09:30 AM Thread Starter
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Thanks for the feedback. I'll bring it up with the dealer service department on the first oil change. I am afraid though that they will tell me they don't feel it. It's almost like a tugging feeling, very short little hesitations and then recovery ...almost staccato.

I'm hope a few more folks that have 2014 2.5i chime in before I see the dealer.

Either:

1) Yes, it feels a little jerky on acceleration (and is fine at speed).

- or -

2) It smoothly accelerates with no hiccups whatsoever.
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post #5 of 209 (permalink) Old 06-16-2013, 05:03 PM Thread Starter
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Went on a trip today so I got to test it a bit more (it's my wife's daily driver, I just drive it on occasion). It very clearly bucks at low speed when you accelerate from a stop when it is cold, say the first 6 - 8 miles after engine startup. After that, I suppose because it is warmed up, the jerking subsides and is more acceptable. Once up to speed (over 20 mph) there is no issue at all, it's very smooth from that point on.

I thought this might just be a break in period thing but after 1500 miles now it's clearly not going away. Do CVT's need to warm up before they start to smooth out?

(I'm certainly going to the dealer as it is warranty, I just wanted to know if I am alone with this issue or not.... or maybe expecting too much....first Subaru.)
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post #6 of 209 (permalink) Old 08-23-2013, 01:27 PM
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2.5i Prem CVT- gentle bucking at light acceleration

Curious if any other 2014 owners notice a gentle bucking when lightly accelerating. Doesn't happen under harder acceleration. I'm not complaining or concerned, just curious - wondering if this is a trait of the CVT or Boxer engine.

Happy motoring...
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post #7 of 209 (permalink) Old 08-23-2013, 01:48 PM
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I think it is the CVT "shifting" as you gradually speed up. Very subtle, but you can feel it if you are looking for it.

When under heavier acceleration, the CVT is not "shifting" as much because it runs the RPMs up, unlike gentle acceleration where it uses the variation in the transmission to increase speed.

In other terms, under gentle acceleration the CVT is taking baby steps while getting up to speed.

Hope that makes sense to everyone.
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post #8 of 209 (permalink) Old 08-23-2013, 02:17 PM
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GeoJosh is on the money.

You have to remember if your coming off a traditional automatic trans, it takes a little getting used to with the new CVT trans, but once you get the feeling for it, I find it is one of the best transmission I ever had in a vehicle. And believe me I have had many, many vehicles, both auto trans, and manual.

When passing on the highway, just slight pressure on the gas pedal and you are doing close to 75 in no time. No feeling of downshifting like in a traditional trans, the vehicle just goes.

I can only imagine in the future if Subaru makes improvements on it how it will be.
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Last edited by tonyford; 08-24-2013 at 05:24 AM.
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post #9 of 209 (permalink) Old 08-23-2013, 02:25 PM
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Quote:
Originally Posted by tonyford View Post
When passing on the highway, just slight pressure on the gas pedal and you are doing close to 75 in no time. No feeling of downshifting like in a traditional trans, the vehicle just goes.
Try having the turbo

I was passing someone the other day on the highway. Was going 65 behind them, got to a passing zone, gave it some more throttle (no where close to WOT), signaled and changed lanes to pass. When I got in the other lane, not even next to them yet, I was going 90... much to my surprise.

Love the Forester, and Love the CVT. As they say "Love, it's what makes a Subaru a Subaru"
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post #10 of 209 (permalink) Old 08-23-2013, 03:01 PM
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The little shudder could be from the torque converter locking up.

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post #11 of 209 (permalink) Old 08-23-2013, 05:37 PM
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It's been bugging me too. GeoJosh that sounds right. The answer is clear: hard off the line throttle!


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post #12 of 209 (permalink) Old 08-23-2013, 08:46 PM Thread Starter
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I've posted before on this topic but it did not get much of a response, just that others did not have the same issue. I think the OP's description sums it up but I can give more detail from my own experience with my vehicle at 3500 miles. I realize it may be me alone that has this particular issue.

I have found there to be three scenarios with regard to low speed acceleration smoothness, a cold cvt, a warmed up cvt, and then a mystery variable.

Scenario #1 - Cold CVT (fresh start)
There is almost no way to accelerate slowly and evenly. There is a significant bucking that I would describe feeling like an engine hesitation (but it is the CVT). It is very noticeable, passenger heads bobble forward and back at times, and sometimes there are heavy jerks. The only way around this effect is to give a very hard throttle until you reach cruising speed which eliminates/minimizes the bucking but doesn't quite work in my 25 mph neighborhood. Once up to speed however there is no problem, everything is smooth and steady.

Scenario #2 - Warm CVT.
After a significant warm up of an undetermined duration the low speed acceleration bucking effect subsides. It will feel more smooth like others have commented, it is still slightly there but acceptable and easily compensated for with a tad more acceleration. If it could only be like this all the time I would be pleased.

The mystery variable.
The problem in my experience is that the cold bucking effect lasts too long, sometimes well more than 10 - 15 miles. There is no such thing as a smooth drive to the local grocer, it's going to buck and jerk both going and coming, that is until you get to speed then there is no issue (you are no longer accelerating). At other times and for no reason it may smooth out much quicker and be okay, I can't figure out the pattern.

In all cases, once you get up to speed there is no problem, it's smooth and wonderful. The problem is only with trying to accelerate from a stop in any sort of gradual fashion, it's just not a pleasant experience, and especially when the engine/tranny is cold. The one thing that overrides the bucking for me is to heavy foot it off the line until you come up to speed.

I'll be going into the dealer for the first oil change very soon and I will report these symptoms of course but I expect them to tell me that its fine or that they can't find any problem with it. Other than the acceleration issue that I have described it is a wonderful car that drives great and gets fantastic gas mileage. If there was a cure for the low speed acceleration bucking I would be a very happy camper.

(edit: I should add that I'm having no issues at all with deceleration as some folks have noted in other threads.)

Last edited by broken; 08-23-2013 at 09:01 PM.
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post #13 of 209 (permalink) Old 08-23-2013, 08:52 PM
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Makes sense...

The 14 suspension is a bit overly dampened compared to the 13 ( which I owned for a few months ), so it's hard to track it down. This is a gentle bucking, not a decisive shifting point ( which I too notice especially when decelerating). If it is caused by a ratio change in the cvt, I'd say the cvt was rapidly cycling between 2 ratios trying to find the optimum gearing under the moderate load. It almost feels as if the engine was lugging, but the rpm gauge is not showing any duress.

Overall, I much prefer the cvt to the preceding 4 gear automatic which IMO was horribly outdated. The cvt's excellent gas mileage and quiet ride is well worth the upgrade.
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post #14 of 209 (permalink) Old 08-24-2013, 04:16 AM
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Quote:
Originally Posted by broken View Post
I've posted before on this topic but it did not get much of a response, just that others did not have the same issue. I think the OP's description sums it up but I can give more detail from my own experience with my vehicle at 3500 miles. I realize it may be me alone that has this particular issue.
As others posted in that thread, you are experiencing something that is not normal. The advice was to take it to the dealer to have them look at it.

The "bucking" described here, at least what I commented on, is very subtle... not noticeable if you are not looking for it.

Quote:
Originally Posted by gsubaru View Post
The 14 suspension is a bit overly dampened compared to the 13 ( which I owned for a few months ), so it's hard to track it down. This is a gentle bucking, not a decisive shifting point ( which I too notice especially when decelerating). If it is caused by a ratio change in the cvt, I'd say the cvt was rapidly cycling between 2 ratios trying to find the optimum gearing under the moderate load. It almost feels as if the engine was lugging, but the rpm gauge is not showing any duress.
The CVT is not going to have "decisive shifting points" because it is a continuously variable transmission. The transmission is constantly adjusting while you are accelerating, unless it is heavy acceleration in which case it holds the same ratio and runs the RPMs up. That is the whole point of the CVT... it adjusts the gearing constantly to keep the RPMs low, which in turn yields improved fuel economy.

The decelerating issue you both mentioned is, I am assuming, when you feel the car "lunge" forward when you let off the gas. It is essentially starting to engine brake on its own when you completely let off the gas.
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post #15 of 209 (permalink) Old 08-24-2013, 05:29 AM
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Quote:
Originally Posted by GeoJosh View Post
As others posted in that thread, you are experiencing something that is not normal. The advice was to take it to the dealer to have them look at it.

^^This

Could be something simple as an adjustment or a replacement trans installed. Either way it's covered.

No reason to be dissatisfied when spending all that money on a new vehicle.
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