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Well this was a long sad read. 7500 miles on my manual and we just starting noticing these problems. Lagging and bogging in 2nd gear around 1500-2500 rpms then it picks up power again as the rpms go up. I asked my wife if she was noticing it and she said yes. Missing/lagging/bogging is not just the way the car drives. It didn't do this before. So there is a problem.
 

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I experience the same bogging\loss of power on my 19 CVT with 5000km milage. I understand it's a low power engine but it's obviously feel something wrong. Here in Ottawa have heat wave warning with temperature over 35℃. With A\C on, the engine feel like loss power. Will follow\update when I have more information.
 

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I tried to drive my cvt in manual mode after read this post. Here is what I found this morning going to work.
1. Engine power was very sluggish from idle until 4000rpm. Have a significant flat spot around 2500~3000. (Before I thought it is the cvt)
2. A/F ration can go high (22) than my other car include the bmw X1 with turbo engine.
3. I could never make smooth transition in on\off throttle application. The car always jerk a bit no matter how smooth my foot go.

I rather suspect the lugging was throttle body related now.
 

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Hi all, I've been reading through all these post for and decided I need to join this site, as I've had the same issue with my 2018 impreza 5mt. I've logged an enormous amount of data while driving here's what I found. When the engine stumble is present, (2200-3300 rpm) the mass air flow is erratic. I had the dealer swap the sensor out, no change. Reviewed the data again, and found ignition timing drops anywhere from 4 to 20 degrees retarded. I bought the new style PCV valve (the one with the blue paint) and installed. After that the car ran amazing for about 2 days. I recently installed a Baja edition air oil separator from Crawford. I made my own bracket to use a xv one. Car has run great on two trips. When I get home this weekend, I'm going to run a can of intake valve deposit cleaner through the engine, and run the car more. I'll update with pics of AOS install and if stumble is gone. I've discovered that there is enough oil coming through that short PCV hose and getting into the engine causing detonation which causes the knock sensor to pull timing.
 

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I've discovered that there is enough oil coming through that short PCV hose and getting into the engine causing detonation which causes the knock sensor to pull timing.
Welcome to the forums! First of all I have to be the guy who asks what octane of gasoline you typically fill up with...
Second, is the knock sensor located in the intake? (I haven't searched for it myself)... Typically such a sensor just "listens" for detonation, and isn't in contact with oil or intake air.
Is your stumble while accelerating/shifting through gears below freeway speeds, or when in top gear trying to accelerate? I've noticed slight hesitation or what feels like more pedal input is required at times in 5th at say 2750 to accelerate slightly, but never between stoplights/on arterial roads or w/ heavy accel.
Can you recommend an OBD2 plugin/device?
 

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Well I can't seem to figure out how to quote, slicktop, but I started out running 87 octane with up to 10% ethanol. I recently switched to 90 octane with no ethanol, and made no difference. Yes you're correct that the knock sensor listens. It is located on the outside top rear of engine block towards the trans. My theory is that since motor oil has an octane rating of roughly about 40, the detonation that occurs is not enough to throw a fault, but enough to pull timing. I was only seeing a slight change in knock sensor readings, but it may happen so fast the scan tool does not capture it. I have a solus ultra from Snap-On that I use. I'm a heavy duty diesel tech by trade, but do side work on cars for extra cash. Also, the stumble/hesitation, happens randomly, but most noticable during acceleration through the gears, or when pulling up a hill in those rpm.
 

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Since I've been seeing data graphs in my sleep, I have another thought which applies to my previous post about oil, octane, and detonation. If there is that much oil coming through PCV valve, obviously there is an issue with blow by. I had my local dealer do an oil consumption test. They said it was normal. 4 stroke engines are not supposed to use oil. I know they'll say low friction piston rings, thin oil, too much engine braking, etc. Doesn't make sense to me. I'm half tempted to just rip the engine apart and see if there is any crosshatch in the cylinder walls at all. Crosshatch being the "sandpaper" that seats the piston rings. Seeing how this is basically a new car (my first new car) I should not have to worry about anything other than regular maintenance and putting gas in it. Sorry for the rant, but I just needed to get that off my chest.
 

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Ratcht80tooth

"...Seeing how this is basically a new car (my first new car) I should not have to worry about anything other than regular maintenance and putting gas in it. Sorry for the rant, but I just needed to get that off my chest..."


Understandable

Good luck.
 

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The root of the subject operational "problem" is most likely only related to two factors, OEM programming and user knowledge.

This '19 is my sixth one with a CVT in the last seven years, two NA and four FA20DITs. I learned quickly to stick to a startup routine that ensured my CVT vehicles operated smoothly every time. Failure to respect this routine almost always meant putting up with notchy performance until it thoroughly warmed up on the road. Now, it's habit and my cars have worked perfectly, with no surging, funky power deliveries nor driveability issues of any kind.

Knowing that these cars are CAN bus systems where the entire car becomes one big computer system with all sensors (throttle angle, temp sensors (air and fluids, e.g.) and ECU-operated devices (engine and CVT, e.g.) must be recalibrated upon each and every startup regardless of where or when the startup is initiated reveals the reasoning behind my observations. Let it do its thing "or else"... else it doesn't work right initially. Because the calibration was cut short and thus "calibrated" to an engine reality that doesn't match ambient reality, it operates poorly for a time after driving away. Otherwise keep your foot on the brake and throttle pedals simultaneouslyl to keep from the unintentional.

Startup has been this way for a long time but it was the advent of CVTs and CAN bus that almost mandated adhering to the reality of the vehicles' requirements. Using an OBDII reader to monitor engine functions confirms the obvious, if driver observations are aren't enough (such as those in this thread).

The startup is simply this; Start engine and do not touch the accellerator, wait until the idle drops and smooths out. Once the engine is running smoothly at a normal low RPM you can drive off smoothly every time.
 

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The root of the subject operational "problem" is most likely only related to two factors, OEM programming and user knowledge.

This '19 is my sixth one with a CVT in the last seven years, two NA and four FA20DITs. I learned quickly to stick to a startup routine that ensured my CVT vehicles operated smoothly every time. Failure to respect this routine almost always meant putting up with notchy performance until it thoroughly warmed up on the road. Now, it's habit and my cars have worked perfectly, with no surging, funky power deliveries nor driveability issues of any kind.

Knowing that these cars are CAN bus systems where the entire car becomes one big computer system with all sensors (throttle angle, temp sensors (air and fluids, e.g.) and ECU-operated devices (engine and CVT, e.g.) must be recalibrated upon each and every startup regardless of where or when the startup is initiated reveals the reasoning behind my observations. Let it do its thing "or else"... else it doesn't work right initially. Because the calibration was cut short and thus "calibrated" to an engine reality that doesn't match ambient reality, it operates poorly for a time after driving away. Otherwise keep your foot on the brake and throttle pedals simultaneouslyl to keep from the unintentional.

Startup has been this way for a long time but it was the advent of CVTs and CAN bus that almost mandated adhering to the reality of the vehicles' requirements. Using an OBDII reader to monitor engine functions confirms the obvious, if driver observations are aren't enough (such as those in this thread).

The startup is simply this; Start engine and do not touch the accellerator, wait until the idle drops and smooths out. Once the engine is running smoothly at a normal low RPM you can drive off smoothly every time.
My theory on the oil coming through the PCV valve is incorrect, as the problem returned today. I am also pretty sure the startup calibration is out as the cause too, because I almost always wait until that little blue coolant temp light goes out before I drive, also my car is a manual and not a cvt. The problem shows up usually after 30 minutes or so of continuous driving. For example, today it started about 35 minutes into my drive home, I was frustrated, and began driving the car like I stole it (running the engine up to 6000 rpm through the gears) after about 10 minutes of this, the problem disappeared. Any idea if the dealer will reflash the ECM if I ask them to? (Last time I mentioned software they said it was up to date). Also I've not yet had a chance to run the intake valve cleaner through the engine yet, and I have to modify my AOS bracket to prevent rubbing before I post pics.
 

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My theory on the oil coming through the PCV valve is incorrect, as the problem returned today. I am also pretty sure the startup calibration is out as the cause too, because I almost always wait until that little blue coolant temp light goes out before I drive, also my car is a manual and not a cvt. The problem shows up usually after 30 minutes or so of continuous driving. For example, today it started about 35 minutes into my drive home, I was frustrated, and began driving the car like I stole it (running the engine up to 6000 rpm through the gears) after about 10 minutes of this, the problem disappeared. Any idea if the dealer will reflash the ECM if I ask them to? (Last time I mentioned software they said it was up to date). Also I've not yet had a chance to run the intake valve cleaner through the engine yet, and I have to modify my AOS bracket to prevent rubbing before I post pics.
Sorry. Other than to suggest cleaning your MAF... not going to comment further.

Best of luck. There's always an answer somewhere.
 

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My theory on the oil coming through the PCV valve is incorrect, as the problem returned today. I am also pretty sure the startup calibration is out as the cause too, because I almost always wait until that little blue coolant temp light goes out before I drive, also my car is a manual and not a cvt. The problem shows up usually after 30 minutes or so of continuous driving. For example, today it started about 35 minutes into my drive home, I was frustrated, and began driving the car like I stole it (running the engine up to 6000 rpm through the gears) after about 10 minutes of this, the problem disappeared. Any idea if the dealer will reflash the ECM if I ask them to? (Last time I mentioned software they said it was up to date). Also I've not yet had a chance to run the intake valve cleaner through the engine yet, and I have to modify my AOS bracket to prevent rubbing before I post pics.
Hello All, joined the forum just for this thread. I've been posting and researching on different forums trying to find the solution to this issue. I'm experiencing the exact same intermittent bog as others describe here. I have taken OBDII data during the bog and the following happens almost simultaneously: AFR commanded and measured drop in the 12's, Timing retards to about -5 and holds, MAP stays around 14psi, throttle position sensors show WOT, MAF sensor fluctuates between 60g/s and 20 g/s. I have captured this while i'm at about 3K rpm in cruise control holding 72mph. I can understand the skepticism of those that say we should be running them harder and step on the gas but this car (and many others with the manual) have a real issue. I"m a little bit of an invader on this page since i'm running an 18 Crosstrek 6MT but the Impreza is such a close sibling couldn't resist jumping in. I have multiple feelers out to Subaru tuners and various mechanics to try and help. no codes, no CEL. Can't figure out what's triggering but i have a strong suspicion the MAF is trying to tell me something. I bought a new one and switched it out just like the gentleman above but the same fluctuation occurred. I can't understand what could cause it to fluctuate other than vacuum leak, electronic throttle fluttering, intake valves, PCM problem, or some type of EGR leak. Let's keep searching and figure this thing out. If I learn anything in my exploits I'll be sure to pass along.
 

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Hello All, joined the forum just for this thread. I've been posting and researching on different forums trying to find the solution to this issue. I'm experiencing the exact same intermittent bog as others describe here. I have taken OBDII data during the bog and the following happens almost simultaneously: AFR commanded and measured drop in the 12's, Timing retards to about -5 and holds, MAP stays around 14psi, throttle position sensors show WOT, MAF sensor fluctuates between 60g/s and 20 g/s. I have captured this while i'm at about 3K rpm in cruise control holding 72mph. I can understand the skepticism of those that say we should be running them harder and step on the gas but this car (and many others with the manual) have a real issue. I"m a little bit of an invader on this page since i'm running an 18 Crosstrek 6MT but the Impreza is such a close sibling couldn't resist jumping in. I have multiple feelers out to Subaru tuners and various mechanics to try and help. no codes, no CEL. Can't figure out what's triggering but i have a strong suspicion the MAF is trying to tell me something. I bought a new one and switched it out just like the gentleman above but the same fluctuation occurred. I can't understand what could cause it to fluctuate other than vacuum leak, electronic throttle fluttering, intake valves, PCM problem, or some type of EGR leak. Let's keep searching and figure this thing out. If I learn anything in my exploits I'll be sure to pass along.
I'm currently going over ground connections, making sure they are clean and tight. I found a couple that are mounted on painted surfaces, but none so far has corrected the issue. I have a couple more to get to though.
 

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Wow, this thread seems to have picked up again after I already traded in my Impreza lol.

I can say for sure though that the MAF sensor is most likely not the issue. I tried replacing mine, I tried cleaning the old one. No difference. I even cut the charcoal filter out of the air box just incase it was some kind of weird air restriction, no difference either. I have a feeling this is entirely a software based problem, the sensors are all reporting the correct data, there is likely just some code that is not doing as Subaru had intended when the wrote it (probably a missing semi-colon somewhere lol) I'm sure one day it will get fixed with a flash at a dealership, unfortunately I wasn't interested in waiting around for that, Subaru got me on this one, I won't make the same mistake again though!
 

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Might I suggest to you guys that you send your data to Subaru? I have seen over the years where Subaru actually listens to the customer, dunno if other car manufacturers do that but I know Subie does.
 
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