('14+) 15 XT Engine/CVT Bucking/Kicking while driving up hill - Subaru Forester Owners Forum
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post #1 of 12 (permalink) Old 06-18-2017, 10:03 AM Thread Starter
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15 XT Engine/CVT Bucking/Kicking while driving up hill

15 XT: Engine/CVT Bucking/Kicking violently while driving up hills

Hey Everyone, Just finished a 1000 mile road trip through the Black hills in South Dakota. Right before breaking 70,000 miles on Saturday I experienced a jolting, kicking CVT symptom while driving uphill that reoccurred intermittently all the way home.


First, some Background about the car and situation:

2015 Forester XT 70,000 miles

Vehicle packed with camping gear, 1 additional passenger and a tiny dog. The car was not excessively weighted. (It drives me CRAZY seeing people with bottomed out rear suspension on road trips so I am very picky about what I bring with me) that being said, it is worth mentioning it was under some increased load.

2016 ECM recall was performed before I purchased the vehicle and is documented in "My Subaru.com" - WQW58 - "WQW58 '14-'15 Forester DIT Pre-Ign Service Program"

Slightly rough idle at start has existed all winter, engine hiccups, shakes for about 30 seconds before smoothing out (or smooths out with gentle throttle input) hadn't thought much of it since it was -50 degrees here in North Dakota and attributed it to the cold. But now after this weekend it seems worse at start.

Paddle shifters were used the morning prior to the issue starting to downshift to 3rd, sometimes to 2nd to save the brakes on steep descents


Bucking Problem: The black hills have some awesome roads, and some are pretty steep. I spent most of the weekend in Sport or Sport# because it felt like the engine was under less stress during the climbs. Saturday While in Sport mode and driving uphill there was a jerk/ kicking feeling at around 60 mph. So bad that my wife looked over at me funny. It jerked and kicked forward violently several times, as if the CVT were unable to decide what gear to be in, or the engine was misfiring. It felt like someone kicking the back of my seat hard and the car jolted forward roughly and would not accelerate smoothly. This problem continued intermittently all day, always while going uphill.

The more steep the hill, the worse the kicking. We drove about 500 miles home that night across North Dakota, the jolting seemed to stop if you went 80mph and used cruise control, but it still happened a few times while going up gradual inclines (cruise control off) also, keep in mind North Dakota is almost totally flat so its much less noticeable.

Summary:

-bucking while accelerating or maintaining speed uphill
-It happens in "I" mode but is less violent
-Happened first while in "S" Mode
-Most violent kicking is in in S# Mode, so I avoided it the rest of the day
-engine braking with paddle shifters was used to descend hills the morning prior to, and leading up to the issue starting
-91 premium fuel only


Stupid Question: Does anyone else use paddle shifters to downshift a gear or 2 on steep declines? Is this ok/not ok to do?


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post #2 of 12 (permalink) Old 06-18-2017, 10:51 AM
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If I were to ever downshift on decent or while slowing down, there is no way it would ever be for reason of saving brakes.

Stan


Shocks > struts.
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post #3 of 12 (permalink) Old 06-18-2017, 11:03 AM
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2 questions.. Is car regularly maintained? Have u performed the 60k mile service including the change of front and rear diff fluid and spark plug?

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post #4 of 12 (permalink) Old 06-18-2017, 11:17 AM
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Could be vacuum/boost leak, or CVT problem. If it was a misfire, I'd imagine there'd be a check engine light warning.

Stan

Shocks > struts.
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post #5 of 12 (permalink) Old 06-18-2017, 12:32 PM Thread Starter
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Quote:
Originally Posted by stan_t View Post
If I were to ever downshift on decent or while slowing down, there is no way it would ever be for reason of saving brakes.

Stan
I should have specified that it wasn't so much to slow myself down, but instead I would slow way down with the brakes, shift to 4th or 3rd respectively using paddles, and ride 3rd gear down a steep hill using brakes here and there as needed. Like how you would with a manual.

Also, that's a good point about the misfire as there are no codes or CEL.
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post #6 of 12 (permalink) Old 06-18-2017, 01:34 PM
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Sounds reasonable to keep the revs up to maintain control. Interesting issue.

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post #7 of 12 (permalink) Old 06-18-2017, 01:45 PM Thread Starter
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Quote:
Originally Posted by SubiJake View Post
2 questions.. Is car regularly maintained? Have u performed the 60k mile service including the change of front and rear diff fluid and spark plug?
I purchased the car at 55k miles last year from a Subaru dealership in NJ. I have done Oil every 3000/ 4000 miles since then. It was Certified Pre owned so I assumed as far as Fluids and stuff it was probably squared away. Maybe someone can shed some light on how serious the "152 point inspection" is, and whether or not preventative maintenance is preformed.

For example I wonder if they would have replaced spark plugs, or just have called em "good enough" at 55k

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post #8 of 12 (permalink) Old 06-18-2017, 01:52 PM
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Quote:
Originally Posted by SubiJake View Post
2 questions.. Is car regularly maintained? Have u performed the 60k mile service including the change of front and rear diff fluid and spark plug?

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This^^ Approaching 70k you need to know if your plugs/cvt have been maintained.

From what ive seen, while u prob need plugs, sounds more like a cvt issue. Uphill extra load placing stress on old fluid, simple as that. Get both changed out asap.

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post #9 of 12 (permalink) Old 06-18-2017, 01:58 PM
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I'm thinking the diff fluid... Front and back since they need changing at every 30k miles. Whereas cvt fluid doesn't need changing til probably 100k miles.. Obviously depends on use but I'm trying to isolate issues based in normal use

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post #10 of 12 (permalink) Old 06-18-2017, 03:27 PM
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I've experienced what I'd describe as light bucking, or a "kick in the seat" feeling at highway speeds. It's only happened a handful of times, so I'm not sure I can narrow down what conditions cause it, but it seems to be while accelerating at relatively low RPM, but at moderate boost (8-10psi).

I'm only at 22K miles and I've already done both front and rear diff fluid change, so I don't think it's related. Seems too early for something CVT-related, but I don't know...

If it gets worse or more frequent, I'll think about taking it to the dealer while it's under warranty, but as it is, it's not something I can reproduce on demand.

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post #11 of 12 (permalink) Old 06-18-2017, 06:50 PM
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Unchanged diff fluid shouldn't cause anything like that, unless the gears grenade themselves, and it takes a lot more abuse to cause that.
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post #12 of 12 (permalink) Old 06-18-2017, 10:22 PM
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It sounds like you guys with the problem need to have a read of this thread Mild surging feeling under light acceleration

This problem is across most if not all model years of the SJ XT.

There is a ECM reprogram for it in the US to fix this or to drastically reduce it.

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