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'17, O.Z. Ultraleggera, K&N filter, tints, LED lights, cup phone holder
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Discussion Starter · #1 ·
Just wanted to see if anyone with high mileage can share their experience with carbon build up. Or anyone who has had issues at all with carbon build up. Would be nice to know when problems might arise
 

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'17, O.Z. Ultraleggera, K&N filter, tints, LED lights, cup phone holder
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119 Posts
Discussion Starter · #3 ·
Yes, I was part of such a thread regarding rattles. That was ultimately solved via premium gas or heat shield. As for BG, it's not quite what I'm asking. Trying to see when various issues arise. I'm still at 50k after 5 years of driving. Not sure if that makes any difference.
 

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2019 Base CVT + Eyesight + Fogs
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797 Posts
decarbonizing did nothing for the rattles. I had the whole engine spark plugs fuel injectors cleaned or replaced under warranty and the pinging continued. That said, if you're under warranty and want carbon cleaning go in there with a tank of 87 and tell them it pings they will clean it per tsb.
 

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2021 Subaru Impreza 5-Door Sport 5MT
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582 Posts
I would recommend the Subaru top engine cleaning kit or some sort of GDI spray that you can put in through the port direction above the throttle body every 12k-18k miles. This will help slow the issue down. Eventually it can/will get bad enough that the vehicle could knock, misfire, etc. Just second nature to GDI engines without multiport sprayers.

Keep in mind, gasoline quality varies by state. 87 in California vs 87 in Indiana aren't always apples to apples. If you're seeing better results with 89+, then keep doing that. I'd also recommend an engine oil that is protectant against LSPI to help with any pre-ignition issues that small displacement/GDI engines tend to suffer from. All of these things combined can help combat pinging/rattling from all angles.
 

· ModFather
2019 Subaru Impreza Sport 5 Dr. Manual Shift
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1,747 Posts
I have a catch can, lots of debate if it will do anything or not. I decided to install one. I figure it can't hurt

ADD W1 Catch Can install - 2019 Subaru Impreza

The Subaru Top Cleaner is a good idea, I have used this STP product in the past:

Liquid Bottle Fluid Automotive tire Personal care

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I have not had any issues myself but the thing is unless you do this type of PM starting early on to prevent buildup from getting too bad, I'm not sure short of walnut blasting , it will remove significant amounts.
 

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2021 Subaru Impreza 5-Door Sport 5MT
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582 Posts
I pulled my intake manifold at 100k to do a look and clean. I typically fill up with Costco or Citco 87 and every so often run 93. Also running Mobile1 every 5k. So here’s a before and after.

View attachment 29442
Thanks for the post. I wish fuel and oil types were strong contributors to this but its not. Until OEM's go to DI and Mutliport on everything this will always be a maintenance item.
 

· ModFather
2019 Subaru Impreza Sport 5 Dr. Manual Shift
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Thanks for the post. I wish fuel and oil types were strong contributors to this but its not. Until OEM's go to DI and Mutliport on everything this will always be a maintenance item.
Sad but true :( It's not like they don't already have a motor set up like this. My 2016 BRZ was that way.
 

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I pulled my intake manifold at 100k to do a look and clean. I typically fill up with Costco or Citco 87 and every so often run 93. Also running Mobile1 every 5k. So here’s a before and after.

View attachment 29442
Something like this should be a big issue with manufacturers. When you do ALL the maintenance and this happens it should be taken care of as a warranty repair especially if it is causing an issue. While I know this is never going to happen, maybe they should add this as a maintenance item just like oil, air filter, plugs, brake fuild, etc... "Every XX,XXX miles this needs to be done." Never gonna happen though. It makes the TCO of the vehicle higher.
 

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Thanks for the post. I wish fuel and oil types were strong contributors to this but its not. Until OEM's go to DI and Mutliport on everything this will always be a maintenance item.
I posted oil/fuel because it usually comes up. I spent many years as a flatrate tech for a few German brands. I’ve done many…many… too many carbon cleans. That is why I pulled mine. I will say my engine was not as bad as I thought. Manufactures do run other injection types, just not in the US. This all took me a couple hours. Just came across this post and figure I’d share my findings.
(Also note there are blades that go in these ports which had a layer of carbon on them which were also cleaned)
 

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Something like this should be a big issue with manufacturers. When you do ALL the maintenance and this happens it should be taken care of as a warranty repair especially if it is causing an issue. While I know this is never going to happen, maybe they should add this as a maintenance item just like oil, air filter, plugs, brake fuild, etc... "Every XX,XXX miles this needs to be done." Never gonna happen though. It makes the TCO of the vehicle higher.
It is being taken care of, electric cars don’t get carbon build up 😂 I’m kidding, but it’s true. I can’t wait to see what joys an electric world will bring, especially in the northeast.
 

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It is being taken care of, electric cars don’t get carbon build up 😂 I’m kidding, but it’s true. I can’t wait to see what joys an electric world will bring, especially in the northeast.
I almost bought an AWD Tesla 3 instead of the Impreza but it would have cost me ~$6k more and I made a lot less than I do now. Part of me wishes I did and the other is happy I didn't. I barely drive now though my wife drives ~80 miles a day. For her, it would have worked out. For me, not so much.
 

· ModFather
2019 Subaru Impreza Sport 5 Dr. Manual Shift
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I'm at about 19K miles on my 2019 Impreza. I've installed a catch can, debatable if it helps but I think it may help some but not eliminate it. I also want to do the Intake valve cleaner every 20K miles. I think if you start cleaning early it might help prolong the enviable.
 

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2020 Subaru Impreza cvt base sedan w//ES
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281 Posts
Daughter's 2020 is at 36k now with 6k ocis. once a month she'll top off with 89 or 93. This spring, we're going to do the crc gdi ivd cleaning thing before her spring oil change. or maybe some liqui moly valve clean into the throttle body.
 
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