5th Gen Subaru Impreza Forum banner

21 - 39 of 39 Posts

·
Registered
Joined
·
16 Posts
Saimsk, you're just setting yourself up for a long frustrating future... IMHO. When the solution to your stated gripe is so very simple... higher octane. Sometimes it is in one's own best interests to step back and get some perspective.

I already know before I own a vehicle that I'm going to use a higher grade of gasoline than what the "book" says to use. There is more than 60 years of driving behind that decision, most of those years having to do with the performance side of cars of one kind or another. Many cars, many years, and there has never been a car that didn't work best with a higher grade of gasoline. It's fundamental to how engines work.

Manufacturers' "recommended" is rarely the "best." It'll get you by. From the air in your tires to the gas you put in it to the care and maintenance... they give you a baseline of what to do, the MINIMUM you need to do. NOT the best thing you can do.

It's up to you to know the difference.

Maybe what's up with your discontent is something else... like not really liking the car or being sorry you bought it instead of something else you really want. In that case, and it happens all the time, cut the frustration out of your life and attack the real elephant in the room... get rid of the car asap and move on.

I put higher octane in my cars for one simple reason... it allows the engine to work at its best. I know that I've done everything I know to eliminate anything less than my engine's maximum without worry circumstances may combine to hurt it... in other words, suffer detonation or worse. To that same end I make certain it's otherwise taken care of as well, with clean filters and the best oil and all the rest. I wouldn't have decided to own it just to get the least from it. I want ALL my car has to give, for as long as I own it AND to have the most value left when I get rid of it.

No one nor no thing ever does its best or lasts as long by getting minimum care.
It's not like that, man.

I love this car. The reason I'm so frustrated is because I love this car.
It's the best vehicle I could buy for the price in the segment with all the tech that I needed such as a large info screen with Android auto, eyesight active cruise control, dual zone climate control, alloy wheels etc etc. It's very comfortable and I think it is a very pretty looking car. But I'm just trying to cover my bases when it comes to any damage that has been done to the car as a result of the first service at subaru. Like I said, the knocking only started when I got the car back. It had the same 91 RON petrol in it when I handed it to them and when i got it back. And like I said, I don't mind using 95 or 98 RON in it. Just that I don't understand why it's started knocking all of a sudden. It's only a year old and I drive it 99% of the time on highways.
Plus, that's not the only problem since my service. There's also a strange whirring/whistling noise in the cabin when I'm coasting on the highway, noise goes away when I apply throttle. Comes back when I let go. Almost sounds like a field of crickets continuously making noise or like some kind of air leaking. It overpowers the cabin.
There's also a slight loss in fuel economy but I'm not too worried about that for now.

I plan to keep this car for the 300,000 km mark but with the current state of the car, I'm not very confident. Since it's still under warranty, I'd like to make the most of it and get what I paid for
 

·
Banned
Joined
·
417 Posts
Thank you a lot for that, I understand now. I hear you.

What service was performed? I'm unfamiliar with the term "first service." I can't imagine anything done in a routine check of things, new oil and filter possibly? How many miles on it, is it a CVT or MT?

Regardless, I've listened to your video several times, and if what I "think" you're referring to is that knocking sound... it has nothing to do with gasoline. It sounds, what little I could make out, almost like rod knock. That would be bad. Bad bad.

Or of course it could be a resonance, something loose or too close to something. But it seems too engine and rpm... and off load... related for that, If it were rod knock, however, it would manifest itself idling. Which you haven't indicated it did.

Have you tried finding more out about it yourself? Being told to use higher octane for what I think I heard would be nuts. Of course, maybe I didn't hear right.
 

·
Registered
Joined
·
16 Posts
Thank you a lot for that, I understand now. I hear you.

What service was performed? I'm unfamiliar with the term "first service." I can't imagine anything done in a routine check of things, new oil and filter possibly? How many miles on it, is it a CVT or MT?

Regardless, I've listened to your video several times, and if what I "think" you're referring to is that knocking sound... it has nothing to do with gasoline. It sounds, what little I could make out, almost like rod knock. That would be bad. Bad bad.

Or of course it could be a resonance, something loose or too close to something. But it seems too engine and rpm... and off load... related for that, If it were rod knock, however, it would manifest itself idling. Which you haven't indicated it did.

Have you tried finding more out about it yourself? Being told to use higher octane for what I think I heard would be nuts. Of course, maybe I didn't hear right.

So it's a brand new car I bought last year, a Subaru Impreza 2018 CVT model.
The first service is the 1st service interval so it's every 12,500 km or 1 year, which ever one comes first. I had the service 4 months ago when the car reached 12,250 ish km(had it done a bit earlier due to work commitments that month). When I picked up the car back from Subaru, while driving it back home, I heard this knocking and rattling noise under load when accelerating at low speeds. The higher octane does remedy it but this was never a problem before the service. It ran totally fine.

hope that helps :)
 

·
Banned
Joined
·
417 Posts
Perfectly clear.

And that's quite a noise. I'm with you, something isn't right. Keep at it until it's fixed. Let us know. Good luck.

One thought... the only thing I can think of that would suddenly cause detonation is unmetered air making the car run too lean. There is only two places where it could rationally get in, and they're the two joints in the intake. One clamp at the airbox and one up at the throttle body. Ensure both fittings are pushed securely in place and the clamps are tight. Also check your airbox clamps, they might have changed the air filter and done something in that area. The MAF is located there, too, so make sure its connector is securely seated.
 

·
Registered
Joined
·
16 Posts
Perfectly clear.

And that's quite a noise. I'm with you, something isn't right. Keep at it until it's fixed. Let us know. Good luck.

One thought... the only thing I can think of that would suddenly cause detonation is unmetered air making the car run too lean. There is only two places where it could rationally get in, and they're the two joints in the intake. One clamp at the airbox and one up at the throttle body. Ensure both fittings are pushed securely in place and the clamps are tight. Also check your airbox clamps, they might have changed the air filter and done something in that area. The MAF is located there, too, so make sure its connector is securely seated.
Yeah, that's my suspicion as well. That they didn't place together the intake system properly or knocked something to cause a leak or if a valve is malfunctioning. It's strange. I'll look into it more and update when ready.

At the moment I've asked Subaru Australia to either fix the car, give me another Impreza or a refund. Let's hope they come back
 

·
Registered
Joined
·
16 Posts
Agreed. It does depend on the dealer as well. Any knocking on a new car is unnerving. Good thing you are coving your bases - if anything is wrong with the engine you’ve covered yourself by seeing the dealer and keeping notes. Curious to see how the warranty claim goes - let me know how it goes if you wish. Best of luck.
Oh btw, idle is fine. No problems when idling and no knocking/pinging when using higher grade fuel. It seems to me like air is leaking into the engine but it doesn't throw any codes. I bought a bluedriver off eBay and check for codes whenever I drive it. All the other details on the app, I can't really understand so not sure if something is abnormal haha
 

·
Registered
Joined
·
16 Posts
Subaru had my car for two weeks. Turns out it's carbon build up in the engine. It's so strange. Is a brand new car at less than 20,000 kms and I've mostly driven it on highways
 

·
Banned
Joined
·
417 Posts
That is disturbing news. It almost doesn't make sense. Of all the things I've read about our Imprezas, this one bothers me the most... because it could be any of us in your shoes.

All I can do, I guess, is keep doing what I've always done... keep adding my MMO and Techron at fillup and keep using top tier 89, run it hard when I get the chance, and stay ahead of maintenance. Then hope my 27 year trouble-free streak stays alive. I like the car too much to start being worried about it.

Glad your car is working right again. I'm going to start researching carbon deposits, I've been avoiding that.
 

·
Banned
Joined
·
417 Posts
If you read my posts you'll note I say something a lot... my focus on fuel injectors and my experience in cleaning them and ensuring they stay that way. I do this for one reason, so that others if they're listing may benefit from that experience.

From inferences you can correctly guess that I am not young, and that I have a long history with automobiles (as well as other motorized things). At my stage in life there's little mystery in a lot of things, and very little in the things I've devoted my life to learning about.

From the beginning fuel injectors have been a lurking constant source of problems in how motors perform. And while gasoline systems have progressed enormously, they're still not perfect nor like to ever be. Even if the gasolines were perfect, however, the reality is that the injectors in all cars become compromised over time and miles, the severity and frequency a variable unique to everyone. However, the same solutions for the root cause of many problems work today as they have from the beginning... keep tthe injectors clean or suffer... sooner or later.

The MMO and Techron "cocktail" that I add at each fillup of the tank is the result of applied research. Look it up. Marvel Mystery Oil is the only way to free stuck apex seals on Wankel engines. It's been the solution for everything from aircraft engines to diesel engines, from cars to standalone oil field motors. Maybe it's the name itself that polarizes the uninitiated, but it truly is their loss if they don't listen. The evidence is scattered throughout the world of all things motor.

I use MMO+T in all my engines, from weedeater and mower to vehicles new and old. The results have been consistently great running motors for many decades. Do yourself a favor and research for yourself... setting aside the tendency toward validation of preconceptions. Listen to the theme running through it all. There are zero downsides and every chance for benefit from useing a time-proven solution for not just carbon deposits like yours, a distinct problem, but also one that can and probably will provide benefits from reduced fuel and maintence costs while running great and trouble free.

The references are endless if you search. Here is a start.

Read this: https://www.motor.com/magazine-summary/carbon-deposits-cleaning-up-whats-left-behind/
 

·
Registered
Joined
·
13 Posts
Subaru had my car for two weeks. Turns out it's carbon build up in the engine. It's so strange. Is a brand new car at less than 20,000 kms and I've mostly driven it on highways
Same issue with me. Brought in twice now: 1) terra clean treatment plus 3 tanks of 91 octane (didn’t work), 2) bottle of induction cleaner by terra clean (didn’t work). I know that carbon build up doesn’t harm the engine per se but it makes an awful noise and effects performance. I am going back to a different Subaru dealer in a few days. Maybe it’s time for a full engine disassembly.
 

·
Registered
Joined
·
269 Posts
If you read my posts you'll note I say something a lot... my focus on fuel injectors and my experience in cleaning them and ensuring they stay that way. I do this for one reason, so that others if they're listing may benefit from that experience.

From inferences you can correctly guess that I am not young, and that I have a long history with automobiles (as well as other motorized things). At my stage in life there's little mystery in a lot of things, and very little in the things I've devoted my life to learning about.

From the beginning fuel injectors have been a lurking constant source of problems in how motors perform. And while gasoline systems have progressed enormously, they're still not perfect nor like to ever be. Even if the gasolines were perfect, however, the reality is that the injectors in all cars become compromised over time and miles, the severity and frequency a variable unique to everyone. However, the same solutions for the root cause of many problems work today as they have from the beginning... keep tthe injectors clean or suffer... sooner or later.

The MMO and Techron "cocktail" that I add at each fillup of the tank is the result of applied research. Look it up. Marvel Mystery Oil is the only way to free stuck apex seals on Wankel engines. It's been the solution for everything from aircraft engines to diesel engines, from cars to standalone oil field motors. Maybe it's the name itself that polarizes the uninitiated, but it truly is their loss if they don't listen. The evidence is scattered throughout the world of all things motor.

I use MMO+T in all my engines, from weedeater and mower to vehicles new and old. The results have been consistently great running motors for many decades. Do yourself a favor and research for yourself... setting aside the tendency toward validation of preconceptions. Listen to the theme running through it all. There are zero downsides and every chance for benefit from useing a time-proven solution for not just carbon deposits like yours, a distinct problem, but also one that can and probably will provide benefits from reduced fuel and maintence costs while running great and trouble free.

The references are endless if you search. Here is a start.

Read this: https://www.motor.com/magazine-summary/carbon-deposits-cleaning-up-whats-left-behind/
I also use MMO. I can't believe how cheap it is to buy given it's proven benefits
 

·
Registered
Joined
·
16 Posts
Here's the report when I got my car back

"ongoing ping check and report to Subaru aus
checked for ping. road tested and recorded data to send to Subaru
Australia.
Sent a video of the pistons to Subaru for assessment. They
instructed
to soak the pistons with SA459, as there was carbon deposits on the
pistons
We replaced the spark plugs and reset engine control unit. Road
fested multile times and there is no pinging evident. Sent off new
data to
Subaru and they are happy with the amount of knock correction. It
is suggested that 95 ron fuel is used to reduce carbon build up"
 

·
Banned
Joined
·
417 Posts
Here's the report when I got my car back

"ongoing ping check and report to Subaru aus
checked for ping. road tested and recorded data to send to Subaru
Australia.
Sent a video of the pistons to Subaru for assessment. They
instructed
to soak the pistons with SA459, as there was carbon deposits on the
pistons
We replaced the spark plugs and reset engine control unit. Road
fested multile times and there is no pinging evident. Sent off new
data to
Subaru and they are happy with the amount of knock correction. It
is suggested that 95 ron fuel is used to reduce carbon build up"
See bolded... that's exactly what I've been saying, and why I use a higher octane than "called for."

Now, if you try the other thing I espouse using to enable better engine running and health you may be able to keep your recently refurbished engine stay working well and trouble free. ;)

4oz Techron (the ONLY injector cleaner that I am certain works) and 4oz of Marvel Mystery Oil added to the tank before and during a full fill of your tank.... with 89AKI/95RON gasoline. :)

I'd say trust me, but we all know how that sounds... but seriously, trust me, it works!!

I know Marvel Mystery Oil sounds like snake oil. But Techron is good enough to be an advertised component of a Top Tier gasoline... although they are the owners of it, they have a right to promote it because it WORKS. MMO, on the other hand, is weird... it undeniably works, but no one seems to know exactly why. And, it's been "working" for decades, curing things nothing else can. Heating it in a spoon with a small tourch finds some of it burning off... but leaving what looks like the same in the bottom that won't boil. Weird. But exactly what we want in a gasoline additive. Although plenty of people add it to their oil, too, to solve gunky issues, I don't because my oil is always new and fresh (3k OCI).

Both things are cheap to try using for a while. Nothing to lose but their small cost. Both are burned perfectly by the engine and cause zero issues, and together (for multiple reasons) they WILL keep the injectors clean and your engine running more efficiently. Really.

I'm happy to hear that all is well with your Impreza again. It's got a fantastic little motor... but it has nothing to give away in inefficiencies. So keep it happy and properly fed, with some "vitamins" to keep it strong. :)
 

·
Registered
Joined
·
24 Posts
I had a 2011 Impreza 2.5i and after 5k miles I started hearing a rattle like a heat shield was loose. I took it in, pre-detonation spark knock. They had a Subaru field engineer look at it and he told me to try mid-grade or high-grade and from a good brand name gas station. I put in high octane for the life of the car and the issue went away till about 150k miles and then came back even with high octane.

However, at about 200k miles, I started to slowly loose coolant into my oil....They said it was the head gaskets, replaced both, I still had the issue so I took it back, then they resurfaced the heads and the problem went away. From what I can guess, the heads were warped from using high octane fuel for the life of the car or they messed up the first head gasket job and had to go back and redo it, resurfacing the heads the second time around like they should've done the first time around.

I'm not a Subaru design engineer but my guess would be that the engine isn't designed to run mid or high-octane fuel for 200k miles and caused the heads to warp. I always used synthetic oil, changed it every 4-5k miles. Always had to add 1qt every 2k miles as it would burn it off over time. So the engine wasn't neglected by any means.

On a positive note, after fixing it, the car now has 270k miles on it. Someone in the family drives it and that was the only thing fixed on it so far.
 

·
Registered
Joined
·
5 Posts
My Impreza 5 has a "engine knock" according to the dealer. They are refusing do anymore service on it without exploring all possible causes of an engine knock. This is clearly a problem 17 Impreza and during the investigation on my car they discovered unusual wear in the timing chain area. Was also told that it was a carbon build up. BS! If you engine is knocking I would have the shop look at your timing and file a complaint.
Subaru had my car for two weeks. Turns out it's carbon build up in the engine. It's so strange. Is a brand new car at less than 20,000 kms and I've mostly driven it on highways
 

·
Registered
Joined
·
71 Posts
Iv always been curious how most cars chug along quite happy on 87 octane all day at 9:1 ish compression ratio but we have 12.5:1 and expected to be ok on the same octane?
 

·
Registered
2020 Manual 4-door Base
Joined
·
83 Posts
So I'm not sure if this is the same "engine knock" problem that some have reported here, but i noticed while idling my car will make a very light knock or tapping noise, but only 1 knock, and then every several seconds it will repeat.

Im not sure if this is something I should take to tbe dealership, i still have warranty.

I dont hear any knocking while driving and defiantly its nowhere as bad or long as the videos posted in this thread
 

·
Registered
Joined
·
27 Posts
Since the OP mentioned being told it was carbon buildup....

The one thing I don't see mentioned so far in this is one solution that all subaru's should have: an Air Oil Separator or Oil catch can. Since these are direct injection engines, the intake valves are not cleaned by the fuel additives since the injectors are inside of the cylinder. I've seen others saying the intake valves could use cleaning every 30k or so. But the real solution is to prevent the engine from spitting gunk on the intake valve in the first place by cleaning the air that the PVC system throws onto the intake valve. Every Direct Injection Subaru should come with an Air Oil Separator IMO.
 

·
Registered
2018 5D Standard Automatic
Joined
·
33 Posts
Since the OP mentioned being told it was carbon buildup....

The one thing I don't see mentioned so far in this is one solution that all subaru's should have: an Air Oil Separator or Oil catch can. Since these are direct injection engines, the intake valves are not cleaned by the fuel additives since the injectors are inside of the cylinder. I've seen others saying the intake valves could use cleaning every 30k or so. But the real solution is to prevent the engine from spitting gunk on the intake valve in the first place by cleaning the air that the PVC system throws onto the intake valve. Every Direct Injection Subaru should come with an Air Oil Separator IMO.
I just bought mine a few months ago at 29k miles, I'm having the same Knock issue that many people in this thread seem to be having, unfortunately I drive for a living and "Just use a higher octane" is a very painful 'solution' (+$40/mo if I can get away with Mid-grade, +$80/mo if I need premium) and am wondering if having my intake cleaned while switching to a better brand of gas, and installing a catch can (in that order) would fix the issue, do you have any recommendations for how I should approach getting the dealer to clean the valves under warranty? Experience tells me if I just tell them to clean the intake under warranty they'll tell me it doesn't need it.
 
21 - 39 of 39 Posts
Top