Carbon Build Up


Autocross Champion
Mableton, GA
2015 GTI
Mikuni, Keihin, or Lectron

Edit: I didn't have anything useful to add that hasn't been said already, so I'm breaking the format a bit haha.


Autocross Champion
HI State
2016 GTI SE MT
Just finished DIY carbon cleaning my 16. 51K miles, 92 octane 99% of the time, short drives (less than 10 miles/day). Took about 5 hrs total. Did not media blast it, used brake cleaner/CRC intake valve cleaner and bushes/picks. Brushes were good only to clean the stems, valves needed scraping with picks and that took about 20-30 minutes each (so 1/2 the total time was just scraping sh!t).


Autocross Champion
Hither and thither
Scattered, smothered, covered, chunked, topped, diced, peppered and capped.

I would be asking to see some codes. Or possibly check with another dealer or independent shop.
As others have said driving habits could play a role or there's another more serious issue at play like pcv or failed coil pack or spark plug issue.
But carbon build up can certainly cause the issues you are having. A good shop should be able to provide "proof" of some sort.

Also I'm just going to out right say it. You don't have a carburetor.

This video explains the carbon build up and clean out process.
What is this, a fucking Wafflehouse?


Go Kart Newbie
SC Sea Islands
2017 GTI S
The dealer has told me I need a carburator cleanout stating the valves are badly coated. My car had only 40K miles. They are saying the carburator cleanout is part of my standard recommended maintenance at 40K. I have put 91 or 93 octane since buying and I have definitely run the RPMs up to blow out the carbon. I cannot find anywhere in the forums where carb cleanout is standard maintenance at 40K and most people report getting to about 75K before having to do it. Yes, I have symptoms but isn't 40K early for this.
2021 GTI SE.

I'd start with an "Italian tune up" 4th gear at 4000 RPM for 20 minutes.


Drag Racing Champion
Hanford. CA
mk7 gti autobahn pp
35k stock tune CA91
15k miles tuned is38 CA91 and e35
I'd say 40k or above you won't be wasting your time by doing the service. Also


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Ready to race!
Frederick MD.
I'll chime in maybe something here will help another. I just did my first carbon cleaning on this car (I did it on my MK5 years back) at 120K miles this was Due to various reasons I had let it go wayyyy to long and was getting cylinder 3 imbalance codes, a terrible misfire at idle, worsening gas mileage and laggie power. I did all the usual stuff - compression test 120 psi in all 4 cylinders (it seems low but could be my crappy gauge but still within limits) Leak down test was good on all 4 - plugs looked good but they were 60k old so swapped them out and I swapped coil packs around to see if the misfire followed, it didn't. That left the injectors and carbon buildup.
all in all it wasnt that hard of a job, the hardest part was removing the hard fuel line from the rail because the flapper vacuum diaphragm on my 2016 fouls the fuel line. I bought a stand off flare wrench style socket - save your money it doesn't work. I found that by using a crows foot on an extension was the best way to loosen and tighten (if you're going to torque you have to take into consideration the extra length).
cylinder 1 had some build up but 2 had nearly nothing (weird) 3 was so caked on and built up it was hard to see the valves at all. 4 was like 1
Why it was like this I dont know. I used gas, CRC and some brake clean ... not all at the same time then hit it with the walnut shell. they weren't quite like new and you could see some carbon "stalactites" when the valves were open but I wasn't about to try and knock them off and into the cylinder. I replaced injector in 3 and resealed all 4 injectors. putting it back together was a fraction of the time to take it apart.
all in all it took me ...... 8 hours - I'm a slow and methodical worker. I broke just one plastic clip that holds the injector connector to the under side of the manifold nothing a zip tie couldn't fix.

Its not a hard job just fiddley AF - I had to loosen the charge pipe from the block and disconnect it at the turbo to get it out of the way - this step is not shown in any of the DIY's

it only took two attempts to start and was smoother immediately. Ive got 500 miles on it now and it idles better the power is back and gas mileage is actually better than when it was new/broken in (34 mpg US) and I drive it .... um "enthusiastically" !

The car is stock btw.