Carbon build up

[Don07]

Good day everyone. I know carbon build up is one of the main issue for IS 250 so I want to know how to address this problem. Anyone have any experience with it? I haven’t encounter any problem at the moment but just for future preference. I saw a video from YouTube that it can only be fixed with walnut blasters, is this correct? When should we start thinking of cleaning the carbon build up? Thank you for reading. Have a nice day. 

Edited November 16, 2023 by Don07

[Linas.P]

I have never seen IS250 in UK that had carbon build-up issue, not sure why, but it seems to be only the issue in US. Yes DI in general has flaws (or I should say car with DI only). I have sneak peaked into my engine before and there was some carbon on intake valve stems, not pretty, but nothing tragic. I have done hydrogen clean on my car and it made absolutelly no difference, if anything one of the emission metrics was 0.1% higher. No change in response or how car drives.

So in short, unless you have issues - forget about it! Much more important would be timely oil changes, 10,000 miles is way too long, I would actually recommend 5,000-6,000 change intervals and never exceed 12 months between changes. I can explain in more detail, but that is kind of different topic... but it does help with carbon build-up slightly as well. Other piece of preventative maintenance you can look at would be "catch-cans"... but cleaning carbon in general is not that you would encounter often on these cars in UK.

[Don07]

25 minutes ago, Linas.P said:

I have never seen IS250 in UK that had carbon build-up issue, not sure why, but it seems to be only the issue in US. Yes DI in general has flaws (or I should say car with DI only). I have sneak peaked into my engine before and there was some carbon on intake valve stems, not pretty, but nothing tragic. I have done hydrogen clean on my car and it made absolutelly no difference, if anything one of the emission metrics was 0.1% higher. No change in response or how car drives.

So in short, unless you have issues - forget about it! Much more important would be timely oil changes, 10,000 miles is way too long, I would actually recommend 5,000-6,000 change intervals and never exceed 12 months between changes. I can explain in more detail, but that is kind of different topic... but it does help with carbon build-up slightly as well. Other piece of preventative maintenance you can look at would be "catch-cans"... but cleaning carbon in general is not that you would encounter often on these cars in UK.

Hello Linas. I am so glad to hear this information. No wonder I only keep hearing this issue from U.S. YouTubers  and car specialists. After knowing this I won’t be too worried about carbon build-up as long as change my engine oil on time per 5,000-6,000. Thank you for your response. Very helpful. 

[RadicalCoupe-Fuji]

I had a VW golf R with DI & too was worried about that until I heard that the EU built ones were fine & it was just a USA problem. Its always good to stretch a cars legs, use the rev range to help clear potential carbon deposits. Think they call it the "Italian tune up" 

[Linas.P]

2 hours ago, RadicalCoupe-Fuji said:

use the rev range to help clear potential carbon deposits

I think that is where DI Only design is in particularly the problem, the "Italian tune-up" kind of works for removing carbon deposits, except from intake valves, because no fuel ever touches intake valves. It still cleans pistons and exhaust valves.

I will expand little bit on oil changes and catch can, and why it is good idea on IS250 (other DI cars as well), so basically because of PCV valve oil vapour with blow by is directed back into intake and that is what ends-up becoming a carbon on intake valves. Replacing oil more often ensures that oil is clean and free of contaminants (like water and fuel that can boil and create vapour) and catch can should collect majority of vapour which would otherwise be routed to intake and clog it. I did not install it on my last IS250 as it was already 120,000 miles when I got it, but there is certainly a benefit of having catch can on lower mile cars. 

As for IS-F/RC-F (and 350) - there "Italian tune-up" works because those engines have both port injection and DI, so fuel basically washes carbon and soot deposits from valves. Fuel additives can also help in such case, whereas they are kind of useless on IS250, just because nothing really touches intake valves, that is the only problem area on IS250, but again - somehow in UK it isn't really that bad. 

[RadicalCoupe-Fuji]

I did find out the problem with engines in the USA, apart from in VW's case the cars we get in the EU are made in Germany at the Wolfsburg plant & in the USA they come from Mexico, the cars we get in the UK/EU have some form of port injection to combat the carbon problem too while the american ones dont. It seems that some of the IS models have port injection too, id just make sure to get one that does. 

[Linas.P]

11 minutes ago, RadicalCoupe-Fuji said:

I did find out the problem with engines in the USA, apart from in VW's case the cars we get in the EU are made in Germany at the Wolfsburg plant & in the USA they come from Mexico, the cars we get in the UK/EU have some form of port injection to combat the carbon problem too while the american ones dont. It seems that some of the IS models have port injection too, id just make sure to get one that does. 

Only IS350... and IS-F

So no, we can't get IS with port injection in UK, DI only. But that said - still not a problem regarding carbon build-up, not unless the car has over 200k miles on it, maybe that is the difference from UK and US, maybe US cars just have so much more miles? That said my last IS250 had 192k when I gave it away and as far as I know still didn't have issues at 208k. 

[H3XME]

+1, no reported Carbon build up issues in the UK.. Just make sure to use super unleaded fuel, it's better for the car.

[Spark plug]

4 hours ago, H3XME said:

+1, no reported Carbon build up issues in the UK.. Just make sure to use super unleaded fuel, it's better for the car.

I agree! mine runs much better on super!

[McShmoopy]

I contemplated this issue myself and tend to agree largely with what Linus says, if it aint broke dont fix it. That being said my car is on 155k miles roughly and because I do plan to keep it for a while I may give the oil catch can a go, you do get some aggressive cleaners in the US that can clean carbon build up when you have an issue but I may stock up on some cheap Mannol intake valve cleaner and put it in every few fill ups when the oil catch can goes in. No harm in it I suppose as well as changing the PCV valve!

The frequent oil changes do make the biggest difference, the logic being the more often you change the fuel the less contaminants are in it therefore no need for things such as engine flush and oil additives, Im cheap and cheerful and keep them to a year irregardless of the miles I do 

[J Henderson]

Interesting video comparing several DI/Carbon cleaners. The products are tested in a controlled fashion, on valves removed from an engine, so "real world" performance might be different. But, on the face of it, they seem fairly ineffective compared to actual physical cleaning (walnut blasting).