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'21 ISM Crosstrek Limited
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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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Smart. When in auto mode the TCU/ECU will always try for the lowest RPM, increasing the likelihood the engine will experience knock. Due to the FA's sophisticated knock detection it will preempt danger and lower the timing... and you will notice that as a "hesitation."

With 93 octane that wouldn't happen.

Keep doing your manual mode thing. You can "outthink" the ECU/TCU and keep the engine in an RPM range that is high enough to match you load, eliminating (most or all) of the timing corrections.
 

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2015 Forester 2.0XT H-CVT
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Smart. When in auto mode the TCU/ECU will always try for the lowest RPM, increasing the likelihood the engine will experience knock. Due to the FA's sophisticated knock detection it will preempt danger and lower the timing... and you will notice that as a "hesitation."



With 93 octane that wouldn't happen.



Keep doing your manual mode thing. You can "outthink" the ECU/TCU and keep the engine in an RPM range that is high enough to match you load, eliminating (most or all) of the timing corrections.


What you are saying makes complete sense as I only have Cali 91 doo doo gas. I guess I’m glad it does this rather than damaging my engine.

So what about base model Foresters that don’t have paddle shifters? Does “L” mode for them fix the problem?


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'21 ISM Crosstrek Limited
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What you are saying makes complete sense as I only have Cali 91 doo doo gas. I guess I’m glad it does this rather than damaging my engine.

So what about base model Foresters that don’t have paddle shifters? Does “L” mode for them fix the problem?


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Unfortunately for them, not so much. L Mode isn't as flexible and its use is limited. No comparison to the XT's CVT controls.

The "hesitation" is almost always related to on-the-fly tune adjustments necessitated by the use of less than optimum octane. Since every tune is designed around a specific and best-case octane, anything less will result in the ECU adjusting timing downward to prevent engine damaging knock in cases where RPMs are too low for the load. When it reduces timing power is reduced, perceived as a dip, or hesitation, in the power being asked for by the accelerator pedal.

Blame mileage mandates, not Subaru. As delivered, the vehicles are safe and fuel efficient with a wide range of fuels. That's the good. The bad is that for many the octane available isn't optimum for the tune, with the consequence being threads like this. I won't comment about those who have the octane available that their vehicles were designed for, but willing choose less... then complain about the inevitable results.

Most here are blissfully unaware of what came before our sophisticates automobiles of today. They might appreciate the minor insults to their ideas of computer perfection if they had to keep some Webers' running right... day to day, season to season, weather to weather, gasoline to gasoline, etc. :)
 

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2017 XT Limited + Tech
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402 Posts
Just curious. Did everyone change the clamps to and from the intercooler mentioned previously? Any improvements?
 

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'21 ISM Crosstrek Limited
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1,177 Posts
Just curious. Did everyone change the clamps to and from the intercooler mentioned previously? Any improvements?
Personally, one of the first things I've done to all my FAs is to tighten all the clamps as soon as I got them. Thus, no issues. In EVERY case there were clamps that needed tightening. Further, because of their design, said clamps need periodic attention and tightening where necessary. The rubber deforms, the clamps do not adjust automatically.

Properly tightened clamps that ensure the integrity of the intake system is imperative. Any slight leak of intake or boost systems will result in the engine working improperly.

Actually replacing the clamps is more a reliability measure. The sleeved clamps both clamp better as well as prevent damage to the hoses they clamp. But there'll be no change in the functioning of the engine between OEM or replacement clamps on an engine with properly tightened clamps.
 
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2016 XT
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283 Posts
Discussion Starter · #346 ·
With 93 octane that wouldn't happen.
iicr, I'm pretty sure there are posters in this thread with the latest ECM patch who say they use 93 and they still suffer from the surging. :shrug: Me personally.. 98 RON stopped the issue. Then way down the line the ECM patch stopped it happening with 95 RON (91 AKI) when the conditions are all present.
 

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2014 Forester XT Touring CVT
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113 Posts
I just started to notice this on the last 2 days of driving home from work. 25-30% throttle, and the RPM's don't seem to be changing. It feels like the transmission is slipping.
 

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2015 Forester XT premium Auto
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88 Posts
I just started to notice this on the last 2 days of driving home from work. 25-30% throttle, and the RPM's don't seem to be changing. It feels like the transmission is slipping.
Ive been having the exact same issue. More noticeable if the car is loaded. Feels like the car is misfiring, but the rpms are steady. Mine started doing this after they did an ecu update. Ive tried resetting my ecu, but issue returns after a couple of weeks. Using sport # makes the symtom go away. Symptom feels like dirty gas or bad plugs.
I just did a top engine clean and swapped my plugs at 36k miles. Hopefully the issue goes away.

UPDATE:
Top engine clean and spark plugs did not make a difference. I figured it wouldnt considering the mileage. I decided to clean the MAF and MAP sensors with CRC MAF cleaner. MAP sensor was really dirty. So far, ive noticed an increase in power and back to its normal smooth delivery of power. I also noticed the RPMs stay above 2100rpm under light acceleration versus not going above 1700rpm before the cleaning. Hopefully the issue doesn’t return.
 

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2014 XT Touring
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7 Posts
I've noticed the pinging twice:

Episode 1: Once last year when I was driving over the steep inclines of Mount Shasta in high temperatures (high 90s). There was no accompanying surging at that time. The episode lasted for seconds and then hadn't happened again until...

Episode 2: I was driving south over the Grapevine in high 90 degree temperatures. I remember seeing the PSI jumping around 8 to 10. Engine oil was 227. Afterward, there was surging involved. At the time, I turned the AC off, slowed down to 50mph and it went away. Both episodes were in regular S mode. Both were using CA Premium 91 octane gas.

I took the car to a mechanic and they said there were no recalls or anything for the car. There's some maintenance that needs to be done like replacing the rear wheel hub bearings but they couldn't reproduce the problem.

After taking the car in, I started internet sleuthing and found this thread. I just got done reading the entire thing. I don't know what to think. I won't not use anything but 91 octane, I'll only use OEM air filters
 

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2015 Forester XT premium Auto
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I've noticed the pinging twice:

Episode 1: Once last year when I was driving over the steep inclines of Mount Shasta in high temperatures (high 90s). There was no accompanying surging at that time. The episode lasted for seconds and then hadn't happened again until...

Episode 2: I was driving south over the Grapevine in high 90 degree temperatures. I remember seeing the PSI jumping around 8 to 10. Engine oil was 227. Afterward, there was surging involved. At the time, I turned the AC off, slowed down to 50mph and it went away. Both episodes were in regular S mode. Both were using CA Premium 91 octane gas.

I took the car to a mechanic and they said there were no recalls or anything for the car. There's some maintenance that needs to be done like replacing the rear wheel hub bearings but they couldn't reproduce the problem.

After taking the car in, I started internet sleuthing and found this thread. I just got done reading the entire thing. I don't know what to think. I won't not use anything but 91 octane, I'll only use OEM air filters
see my update above. its easy to get to the MAP and MAF sensors for cleaning. mine showed no error codes, but it really ran terrible. i also noticed my mpg go from an avg of 22mpg to hitting 28.5mpg.
 

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2015 Forester XT premium Auto
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@Giantdefy is there a guide to cleaning the MAF and MAP sensors?

make sure you use crc MAF cleaner. under $10 from any automotive parts store. the MAF sensor is located by the air filter held on by 2 screws. just unplug the connector, unscrew and pull up. make sure u do not touch the wires or use the wrong chemical cleaners and these are sensitive and cost around $300 to replace. just spray liberally to clean the wires, then let air dry for at least 30 minutes before reinstalling.
the MAP sensor is easy to access. remove the engine cover, 2 plastic pins at each corner towards the back are holding it down, remove those then lift up at the front. the MAP is located in the center of the intake manifold held in by one 10mm screw. unplug it, then unscrew. pull up on the MAP, it will most likely be covered in oil. spray it with the crc cleaner and make sure u get inside the hole. mine was caked in oil. let it air dry before reinstalling. my car ran a lot smoother after doing this.
im adding this to my annual maintenance. this is a super easy DIY that any non mechanic can do.

MAF clean https://youtu.be/lSCtVdZa-xQ

close but not the same map sensor. hopefully u get the idea to clean the wire and inside the tube. https://goo.gl/images/73qTY2

MAP sensor is located where this guy is spraying. he is doing a intake valve cleaning. https://www.youtube.com/watch?v=Rw6FdAPX8ao&feature=share
 

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2014 XT Touring
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Thank you, @Giantdefy. I plan on doing this ASAP.

Out of curiosity and because you obviously have some passion for the car (or for the preservation of your car), can I ask what else you do for your annual maintenance? Thanks in advance!
 

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2015 Forester XT premium Auto
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Thank you, @Giantdefy. I plan on doing this ASAP.

Out of curiosity and because you obviously have some passion for the car (or for the preservation of your car), can I ask what else you do for your annual maintenance? Thanks in advance!
Get yourself a app for your phone to track your maintenance. I use car minder plus, lets me know when maintenance is due. I just follow the Subaru maintenance schedule. I use the app to also track leather care, wiper blades, car waxing etc.
 

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2014 Forester XT Touring CVT
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make sure you use crc MAF cleaner. under $10 from any automotive parts store. the MAF sensor is located by the air filter held on by 2 screws. just unplug the connector, unscrew and pull up. make sure u do not touch the wires or use the wrong chemical cleaners and these are sensitive and cost around $300 to replace. just spray liberally to clean the wires, then let air dry for at least 30 minutes before reinstalling.
the MAP sensor is easy to access. remove the engine cover, 2 plastic pins at each corner towards the back are holding it down, remove those then lift up at the front. the MAP is located in the center of the intake manifold held in by one 10mm screw. unplug it, then unscrew. pull up on the MAP, it will most likely be covered in oil. spray it with the crc cleaner and make sure u get inside the hole. mine was caked in oil. let it air dry before reinstalling. my car ran a lot smoother after doing this.
im adding this to my annual maintenance. this is a super easy DIY that any non mechanic can do.

MAF clean https://youtu.be/lSCtVdZa-xQ

close but not the same map sensor. hopefully u get the idea to clean the wire and inside the tube. https://goo.gl/images/73qTY2

MAP sensor is located where this guy is spraying. he is doing a intake valve cleaning. https://www.youtube.com/watch?v=Rw6FdAPX8ao&feature=share
Awesome! I'll be doing this once it's not 100+ in Texas. Thanks for this update.
 

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2015 Forester XT premium Auto
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I see you have a 2014 xt. Make sure you have subaru perform the ecu update for surging. Bulletin #:11-164-16
https://subaru.oemdtc.com/365/surgi...tures-2014-2016-subaru-forester-2-0l-di-turbo

If u had the bulletin done and still have the surging, then cleaning the MAP shld get you back to a smooth ride.
I've got a 2014 XT myself, just had the ECU update for surging performed, seems to have helped quite a bit. Wish they would mention it to you when you bring it in for service, but they never did until I mentioned it was surging... ah well, at least it's running smoothly again. Might have to try cleaning the MAF and MAP anyways though, probably couldn't hurt :)
 

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2014 Forester XT CVT
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I've seen this thread for a long time but have now only started experiencing the issue at 120.5k miles.
Lately I've been driving in the middle of Texas in 95+ degree heat, 300 mile trips, during the day at 25-30% throttle and 8psi boost - started feeling the surging.
After I began to notice it it's now happening during evening drives as well.

I never had the ecu update for the surging [Bulletin #:11-164-16] as @Giantdefy mentioned. I'll for sure do the MAF and MAP sensor clean and if that doesn't work I'll probably take her in and asks how much the update will cost (any one know cost? since it's not a recall)

I did the new clamps WAY early on in 2014 at around 10k miles. I'll check those too.
 
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