2014 Forester XT Loud Knocking + Power Loss

[gathermewool]

Car: 2014 Subaru Forester XT
Miles:~34k miles
What: Tapping knocking sound upon initiation of boost, engine falls flat on its face (no power.) Then, nothing...
Fuel: 1/4 tank (110 miles left indicated)
Oil: just above full mark (no consumption in the past 7,300 miles of this OCI
CEL: None
Boost: Not noted at the time (boosted fine afterward)
RPM: seemed unusually low when the incident occurred.


I've had my ECM updated in the past for a hard/long-start issue (it would crank for 5+ second before starting and sometimes even crank until it timed out.) The reflash fixed this issue.

I've more recently had my ECM updated for the low-speed knock that I never experienced (I actually received a letter from Subaru for this one.) Well, that is until today...

We drove the car 15 minutes to check out some replacement exterior doors without any issue, at 35-50 MPH the entire way (oil temperature reached 180F+. When we left, there was a little bit of traffic, but not much. To ensure I didn't slow anyone down I got onto the road and gave it maybe 30-50% throttle (this engine typically revs to 2.5k RPM+ with little to no boost and then ramps down to lower RPM and higher boost)

Not this time: As soon as I accelerated I heard the loud :TAP-TAP-TAP-TAP-TAP: and felt the engine fall flat on its face. I let off the gas and looked down simultaneously, and noted that the engine speed was below 2k RPM, unusually low for 30+% throttle. I didn't note boost level.

This vehicle has multiple drive modes, with I (intelligent) being the tamest (lowest throttle response and boost level) and S (sport) mode being a little more responsive. I typically drive in S-mode, only because it starts out a couple of hundred RPM higher at all times than I-mode, so it's more responsive to tip-in. When I switched from I mode to S-mode, everything was normal. I switched back about halfway home and everything was again normal.

The turbo in this engine is twin-scroll, so it boosts very quickly and easily - I didn't intentionally boost on the way home, but it did so all by itself, without falling on its face like previously mentioned.

I've already left a message with the dealer to setup an appointment, but what do you guys think? Flame suit is already on for not pulling over immediately and checking the oil.

 

[Donald]

Sounds like an ECM problem.

 

[gathermewool]

Wouldn't that result in more frequent problems? This update has been installed for the past 1-2 months, I think. The updates were also to fix programming issues, which they reportedly have done.

It's odd that I wasn't experiencing any negative effects which the last update was supposed to cure, but just experienced said event!

 

[CT8]

Bring the car into the shop it is not the oil.

 

[mtndew_dad]

Maybe bad or low octane gasoline. Might have no effect until a fair amount of throttle was applied resulting in knocking followed by a rapid decrease in power via ECM. Or bad sensor.

 

[gathermewool]

Originally Posted By: mtndew_dad
Maybe bad or low octane gasoline. Might have no effect until a fair amount of throttle was applied resulting in knocking followed by a rapid decrease in power via ECM. Or bad sensor.


It's down to 1/4 tank. It hasn't acted up at all in the past 3/4 tank.

 

[Donald]

Originally Posted By: mtndew_dad
Maybe bad or low octane gasoline. Might have no effect until a fair amount of throttle was applied resulting in knocking followed by a rapid decrease in power via ECM. Or bad sensor.


How many people get bad gas these days? The EPA forced all the stations to upgrade their tanks years ago and E10 should keep water in the gas station tanks to a minimum.

 

[RedOakRanch]

The symptoms sounds like on Road Kill when something kept falling off thier turbo at a road race. It was not a Subaru though and I can't remember what it was. Basically I've offered no help so I've flamed myself!

 

[gathermewool]

Originally Posted By: RedOakRanch
The symptoms sounds like on Road Kill when something kept falling off thier turbo at a road race. It was not a Subaru though and I can't remember what it was. Basically I've offered no help so I've flamed myself!

 

[Trav]

Let the warranty take care of it. Post back with what it was if you would.

 

[Andrew1972]

My guess is waste gate flutter or stuck waste gate.

 

[gathermewool]

Originally Posted By: madRiver
My guess is waste gate flutter or stuck waste gate.
Originally Posted By: madRiver
My guess is waste gate flutter or stuck waste gate.


You can't hear the wastegate on this turbo. Also, wastegate flutter sounds like, well, flutter.

 

[JimPghPA]

Just a guess, if it is an automatic, could it be shifting into the wrong gear? Like maybe shifting into too high of a gear. If so, maybe a bad sensor giving the control for the trany the wrong information.

Shifting into too high of a gear would explain the falling on its face/lack of power and the tap tap tap could be the sound of an engine bogging down with too high of a load due to being in too high of a gear.

 

[Superflop]

Knock sensor went ape and pulled the boost to save the motor or at least it thought so. Afterwards no knock so timing and boost came back

 

[Rand]

Originally Posted By: gathermewool
Originally Posted By: madRiver
My guess is waste gate flutter or stuck waste gate.
Originally Posted By: madRiver
My guess is waste gate flutter or stuck waste gate.


You can't hear the wastegate on this turbo. Also, wastegate flutter sounds like, well, flutter.


Clamps leaking? seems odd

 

[JTK]

No check engine light or reduced power light? Any major sensor or component failure would have lit the dash up.

The falling on it's face and noise description sounds similar to what my brother experienced when the turbo locked up on his 2005 Outback. He replaced the turbo and clogged bango bolts himself. I'd have to ask him if he got an CELs at the time.

 

[gathermewool]

Originally Posted By: JimPghPA
Just a guess, if it is an automatic, could it be shifting into the wrong gear? Like maybe shifting into too high of a gear. If so, maybe a bad sensor giving the control for the trany the wrong information.

Shifting into too high of a gear would explain the falling on its face/lack of power and the tap tap tap could be the sound of an engine bogging down with too high of a load due to being in too high of a gear.


It's a CVT, but that is a possibility - very good point, actually. The CVT usually revs up initially and then lowers after you're "off the line" and accelerating. I believe there may be a TCM update out on the street, but I don't recall what it was for and if it might apply.

Originally Posted By: Superflop
Knock sensor went ape and pulled the boost to save the motor or at least it thought so. Afterwards no knock so timing and boost came back


Possible, too, but wouldn't explain the loud tapping noise, would it?

Originally Posted By: Rand
Originally Posted By: gathermewool
Originally Posted By: madRiver
My guess is waste gate flutter or stuck waste gate.
Originally Posted By: madRiver
My guess is waste gate flutter or stuck waste gate.


You can't hear the wastegate on this turbo. Also, wastegate flutter sounds like, well, flutter.


Clamps leaking? seems odd


Also a possibility, and there is a boost-leak fix that includes tightening some intake hose clamps and replacing others. One of the moderators who is pretty involved and knowledgeable with these Foresters mentioned this, but also that the symptom he had when this occurred to him as sounding like a can of marbles, which I associate more with running too low of octane or having an engine in poor tune.

What I experienced was literally a consecutive TAP-TAP-TAP-TAP-TAP, not a bunch of concurrent taps or rattles.

Originally Posted By: JTK
No check engine light or reduced power light? Any major sensor or component failure would have lit the dash up.

The falling on it's face and noise description sounds similar to what my brother experienced when the turbo locked up on his 2005 Outback. He replaced the turbo and clogged bango bolts himself. I'd have to ask him if he got an CELs at the time.


I'd appreciate more information, if he can remember. Bluesubie also had a turbo failure on his Baja that I believe was the result of the infamous turbo oil supply banjo bolt screen. I honestly don't know if this turbo supply has a screen in the supply.

//

I called the service department to describe my issue, how I've had previous issues, and that I was hoping that we could stop by for a quick scan of the ECM/TCM for pending codes, even if they can't do any further trouble-shooting yet. He said that they were busy and couldn't see me until Friday. I then explained that my confidence level in this vehicle is rapidly eroding away after previous issues and multiple ECM updates; and further, that this is my wife's car, used mostly to transport the baby around in, and that I don't feel that she is safe driving it, knowing that she might lose all power when she needs it most.

He got a little snippy and told me to drop it off Thursday night, but my wife got an email with an appointment for Thursday morning.

I also emailed Subaru of America, so they know that this is unacceptable.

 

[sxg6]

From a fellow subaru owner.. I think your engine might be toast, unfortunately. Then again 4th gen turbo engine failures are common over at legacygt.com, so maybe that's why I'm not very optimistic, even though you have a different engine.

 

[Bladecutter]

Originally Posted By: gathermewool

I called the service department to describe my issue, how I've had previous issues, and that I was hoping that we could stop by for a quick scan of the ECM/TCM for pending codes, even if they can't do any further trouble-shooting yet. He said that they were busy and couldn't see me until Friday. I then explained that my confidence level in this vehicle is rapidly eroding away after previous issues and multiple ECM updates; and further, that this is my wife's car, used mostly to transport the baby around in, and that I don't feel that she is safe driving it, knowing that she might lose all power when she needs it most.

He got a little snippy and told me to drop it off Thursday night, but my wife got an email with an appointment for Thursday morning.

I also emailed Subaru of America, so they know that this is unacceptable.


That's a bit much for a 1 time event, that you haven't been able reproduce.

Can you recreate the event by exactly driving the same route you did, exactly?
If you can reproduce it, you can then get the dealer to do the same, and you will then be able to figure something out.

If you and the dealer can't get the problem to reoccur, how exactly do you expect them to "fix your confidence" in your car/their products?

And I have to ask, what other problems have you had with this car, when you've said that you never had this problem before?

BC.

 

[gathermewool]

As expected, the dealer wasn't able to reproduce the issue after having the car for half the day. They did find ANOTHER ECM update, which supposedly fixes a surging problem at high load and high temperatures. Well, it was cool when this occurred and I was accelerating at a middling level on a flat road, so...

The SoA rep got back to me, saying that he spoke with the dealer service manager, and that they both are confident that there is no issue, and that I should "be reassured that Subaru stands behind the engine in [my] Forester for many years and miles under the Subaru power train warranty."

The service writer even insinuated that nothing bad would happen in a '14. I'm sure they don't know what rod knock is, but I'm glad they're so confident.


Originally Posted By: sxg6
From a fellow subaru owner.. I think your engine might be toast, unfortunately. Then again 4th gen turbo engine failures are common over at legacygt.com, so maybe that's why I'm not very optimistic, even though you have a different engine.


I sure hope not.

Originally Posted By: Bladecutter
Originally Posted By: gathermewool

I called the service department to describe my issue, how I've had previous issues, and that I was hoping that we could stop by for a quick scan of the ECM/TCM for pending codes, even if they can't do any further trouble-shooting yet. He said that they were busy and couldn't see me until Friday. I then explained that my confidence level in this vehicle is rapidly eroding away after previous issues and multiple ECM updates; and further, that this is my wife's car, used mostly to transport the baby around in, and that I don't feel that she is safe driving it, knowing that she might lose all power when she needs it most.

He got a little snippy and told me to drop it off Thursday night, but my wife got an email with an appointment for Thursday morning.

I also emailed Subaru of America, so they know that this is unacceptable.


That's a bit much for a 1 time event, that you haven't been able reproduce.

Can you recreate the event by exactly driving the same route you did, exactly?
If you can reproduce it, you can then get the dealer to do the same, and you will then be able to figure something out.

If you and the dealer can't get the problem to reoccur, how exactly do you expect them to "fix your confidence" in your car/their products?

And I have to ask, what other problems have you had with this car, when you've said that you never had this problem before?

BC.


I'm not sure I understand your post. I mentioned that this wasn't the first ECM update to fix an actual problem, along with other updates to fix problems that I wasn't experiencing.

Also, how many times should one experience massive power loss, coincidental with what sounded like rod knock, before becoming concerned? I patiently waited for a fix to cure my annoying, embarrassing, and potentially detrimental hard/long starts. For power loss and rod knock, I have zero patience. Again, this wasn't hesitation and a bit of pre-ignition; what occurred was a nearly complete loss of power as I was trying to accelerate with what sounded like rod knock.

//

We most likely have many more miles in our Forester, but my patience has run thin with all of these updates, and I don't think it's unreasonable to be concerned. What do I expect Subaru to do to fix my confidence? Nothing. Me, I've documented my problem with both the dealer (unreliable, should this occur in the future) and SoA. Should my engine fail just outside of warranty I feel like my own actions and inquiries will give me confidence then to make more of a demand than a request for good will.