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I read something the other day about a class action suit against Subaru regarding fuel pump issues in 2017-2019, the symptoms of which describe a lot of our issues. I too had a recall done last fall, car ran great all winter, and early this summer I started noticing the lugging again.

 

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I read something the other day about a class action suit against Subaru regarding fuel pump issues in 2017-2019, the symptoms of which describe a lot of our issues. I too had a recall done last fall, car ran great all winter, and early this summer I started noticing the lugging again.

Although this seems plausible, if my car’s VIN doesn’t show that it needs a recall (which it doesn’t) in their system, the dealer is going to laugh and turn me away. An overheating fuel pump sounds really really on point. Especially when taking hot ambient temps into account. Please don’t let this issue discussion die!! Keep postin whatever you find/think of
 

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Hi all,

I recently bought a 2017 Impreza Touring 5mt with 29 300km.

Just to chime in with the same issue. When the engine is cool it seems to run nice and smooth but when it has warmed up I get noticeable loss of power and jerkiness around 2000-3000 rpm. Bought a BlueDrive OBDII scan tool and have logged a bit of data. The car really seems to be retarding timing under load as you can see in yellow which would explain the loss of power. Happens in 2nd and 3rd gear but also happened to me on the highway doing 110km/h going up a slight incline. Have an appointment at the local subaru dealer for the 3 recalls that haven't been done yet (PVC, brake lines and ECU flash for the coil pack overheating) so I hope maybe the PCV or ECU flash might help. Have been using 87 octane for know but will have to try using 91 octane as I suspect it must be detecting some knock to retard timing as such (all other sensor info seems fine from what I understand). This is very frustrating and I am starting to regret buying the car... not many choices for small awd cars.
23843
 

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Hi all,

I recently bought a 2017 Impreza Touring 5mt with 29 300km.

Just to chime in with the same issue. When the engine is cool it seems to run nice and smooth but when it has warmed up I get noticeable loss of power and jerkiness around 2000-3000 rpm. Bought a BlueDrive OBDII scan tool and have logged a bit of data. The car really seems to be retarding timing under load as you can see in yellow which would explain the loss of power. Happens in 2nd and 3rd gear but also happened to me on the highway doing 110km/h going up a slight incline. Have an appointment at the local subaru dealer for the 3 recalls that haven't been done yet (PVC, brake lines and ECU flash for the coil pack overheating) so I hope maybe the PCV or ECU flash might help. Have been using 87 octane for know but will have to try using 91 octane as I suspect it must be detecting some knock to retard timing as such (all other sensor info seems fine from what I understand). This is very frustrating and I am starting to regret buying the car... not many choices for small awd cars.
View attachment 23843
I did the same thing with recording data, and had the same timing issue. I had my recalls done a while back, and never recorded data again and it got cold outside and the problem didn't come back until summer. I stopped getting to upset with it, and just chock it up to it is what it is because of emission regulations. Also, I run to rpms up to 4k now in 1st, 2nd and 3rd. Problem seems to not show up then. Fuel mileage really hasn't gone down, and I just drop from 5th to 4th is needed at highway speeds. It does make me feel a little better when I do get frustrated, to just red line the engine through a couple gears though. (y)
 

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I did the same thing with recording data, and had the same timing issue. I had my recalls done a while back, and never recorded data again and it got cold outside and the problem didn't come back until summer. I stopped getting to upset with it, and just chock it up to it is what it is because of emission regulations. Also, I run to rpms up to 4k now in 1st, 2nd and 3rd. Problem seems to not show up then. Fuel mileage really hasn't gone down, and I just drop from 5th to 4th is needed at highway speeds. It does make me feel a little better when I do get frustrated, to just red line the engine through a couple gears though. (y)
Thanks for the info, what octane gas are you running ? Ever try with higher octane ?
 

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I ran 90 octane ethanol free for a while, I'm back to running 87 right now. 90 got too expensive. The octane didn't seem to make any difference though. I'm starting to revisit the idea of buying software to try and tune the ECM myself, but haven't had the time.
 

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I've had the same issue being described start recently. When it was happening every time I went through 2-3k, I made an appointment with the dealership. By the time my appointment came around the problem stopped happening as often and they couldn't replicate it. When it was happening often it was about 90 degrees and I was driving a lot for delivery. Now that it's a little cooler during the weeks it hasn't really been happening anymore. My best guess is overheating somewhere along the line.
 

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From what I gather of all the info I've read and the data collected, heat combined with the high compression ratio of the engine and regular gas leads to a bit of spark preignition (knock) which must be detected by the knock sensor causing the ECU to pull timing hence a loss of power under certain conditions. Now why the problem happens mostly between 2000 and 3000 rpm is probably because of the variable valve timing changing valve profiles (and effective compression ratio) at certain RPMs. I'm having an independent mechanic look at the car next week to see if he can spot anything but if he can't find anything (and I guess he probably won't...) I will then try higher octane gas, reset the ECU for it to relearn and report back. If all that fails I am getting the 3 recalls done in September (earliest the dealer could do) and will see if the ECU reprogramming or PVC valves do anything...
 

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I found this article to be a good read on Subaru's knock monitoring system.

COBB Support

Makes me want to try a fill up with 91 octane, then reset the ECU to try and make it redo fine knock learning and DAM under conditions less likely to knock.

If that doesn't work then maybe replacing the knock sensor ?
 

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Just an FYI, most all of the stuff from Cobb is dedicated to turbocharged engines. It is a good read though. I had read a similar article when I was into this problem deep. I never replaced the knock sensor though. Maybe it'll work. Be sure to let us now if it does.
 

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I’m having the exact same issue on my 2019 Impreza with a manual transmission. Thought I’d share my experience. As it warmed up this summer, I started noticing the issue again, I hadn’t really noticed it this winter. We just got back from a vacation to Colorado, and I was prepared to really have to deal with the stuttering with all the mountain driving. To my surprise, it ran great in the mountains, pulling up hills in the 2500-3000rpm range most of the time without stuttering. What I did notice is if I let it warm up and idle down, it would have plenty of power until I gained say 2000 feet altitude, then I would lose power and have to keep it above 3000rpm. If I would stop at that altitude and let it idle for a bit it seemed like it would learn to be happy again and have good power. Now the strange part: on the way home (to eastern Oklahoma) it started stuttering again as we got to lower altitude. Problem returned in full force. Only thing I can think of is something to do with the oxygen sensor or MAF and the higher altitude. I ran 89 octane most of the time. I don’t think it had anything to do with the cooler temps in CO because it was doing it at 75 deg on the way home and I ran it at hotter than that in CO and it was fine. What’s y’all’s thoughts?
 

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Tried 91 octane with absolutely no difference, was doing it real bad today even if it's not that hot. Going to try the ECU reset. People of the 2018+ Crosstrek forums are having the exact same issue (Model Year 2018 and Newer - Loss of power).

Wondering if it may have to do with the PCV system letting oil vapors into the intake lowering effective octane rating and causing engine knock. Or a problem with the knock sensors themselves. Or with the ECU... Was able to reproduce the problem perfectly today : between 2000-3000 rpm with low throttle is smooth but there is a clear threshold that increased throttle makes it start to lose power and hesitate... actually getting less acceleration than with less throttle. Starting to get quite annoyed with the car ad thinking of selling it.
 

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Actually starting to wonder if there are any people with 2017+ impreza MTs who don't have this problem... is it something up with the ECU's programming ?
 

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Just bought a 2019 MT with 28k mi on it and I'm experiencing this problem. It's really discouraging to see that you guys have been talking about it for the past 3 years and haven't got a solution. Even with the THREE recalls seems like a temporary fix and not permanent. Great! The problem is is that it's actually dangerous, not just a performance issue. You don't give oncoming traffic extra time before turning or getting on the freeway and push the pedal to the floor with no power, eventually someone's going to smack right into the back of you. Hopefully we get some resolution soon. 😭
 

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I haven't ever had this problem with my 2017. I have been running with a tune for over a year to eliminate the rev hang between gear changes. Between 2500 and 3000 rpms the stock tune (and also the modified tune) has a transition to variable valve timing occurring. Maybe there's an intermittent fault with a VVT sensor or solenoid.
 

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I'm very pleased with my tune (each tune is customized based on your requests). I have no regrets. The OEM Subaru tune definitely has some areas that can be improved upon for the manual transmission cars.
 

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For future reference:
Due to direct-injection into the combustion-chambers, anything you put into the gastank will NEVER touch the back of the valves where the crud collects.


The ONLY way for a 'cleaner' to get to the back of the valves would be to feed it into the intake-manifold.

This is the main reason I've installed a catch can. You are right while cleaner will get the injector system clean, in order to clean the other bits with a DI system you need to put cleaner in the intake itself. I've use the aerosol version of Seafoam in the throttle body. Subaru also makes a kit you can google. the liquid version does require a pretty pricey tool to use it though. Part of the trick is to introduce it in a central location that will evenly distribute the cleaner. To me one of the best places is directly into the throttle body. Depending on the intake some of them do have good locations that are nicely centered.
 

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Just a quick update for you guys : This week I tried reseting the ECU and doing the idle relearn procedure explained here.

I was about 1/4 way through a new tank of 91 octane when I did the reset and was getting loss of power beforehand. Since the reset the car has been flawless. Knocking on wood. Maybe the ECU had learnt that certain conditions caused knock when it was ran with a bad tank of gas... maybe even the gas I ran the car with when I got it from the used car dealership as the car must have been sitting on the lot for a while. Anyway, hope this lasts and hope it can help some of you.
 

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Just a quick update to say that since the ECU reset everything has been fine. Got my recalls done last week also with no ill effect. Going to try switching back to 87 octane soon.
 
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