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Direct-injected cars have one major drawback over their port-injected counterparts. That is, carbon deposits build up over time and need to be removed at regular intervals. The most effective and common method to do so is the use of Walnut Blasting. 

Walnut blasting is recognized as one of the safest and most efficient methods of removing carbon buildup from your car's intake manifold and intake valves. Nearly all direct-injected engines will need this process completed semi-regularly throughout the life of the car. The process of walnut blasting is comprised of using crushed walnut shells propelled by compressed air to "chip away" at the carbon build-up. The walnut shells themselves are softer than the metal of your intake manifold and valves, which means that they won't cause damage while being hard enough to remove the deposits. 


Do you really need to walnut blast your intake manifold and intake valves?

Unlike on cars with port injection, where carbon deposits are constantly cleaned off of the intake valves, and runners, cars that use direct injection do not have this luxury. Over time, those carbon deposits build up into a thick layer that can cause some serious issues. That build-up restricts the airflow to your engine and reduces its ability to "breathe." Imagine having a cold and being "stuffed up." Walnut blasting is your car's decongestant. Some of the symptoms of heavy carbon buildup are:

  • Noticeable loss in performance
  • Check engine light on/won't pass emissions
  • Poor fuel economy
  • Rough running

After your intake manifold and intake valves have been cleaned, you should immediately start seeing the benefits. You can expect a smoother idle, lower fuel consumption, smoother throttle response, and even additional horsepower gains. 

If you want to learn more about why carbon buildup happens and specifically why it's most prevalent in direct-injected engines, this video covers it in detail.



How often should you walnut blast your intake manifold and intake valves?

This completely depends on the way in which you drive your car. If you're letting your car fully come up to temperature and then revving out the engine through its entire RPM range, then you'll likely have less buildup than someone who only has a three-minute commute to work. However, it is still recommended that on a brand new car, you walnut blast the intake manifold and intake valves somewhere between 25,000-50,000 miles. After that first initial cleaning, you shouldn't need to for another 40,000-50,000 miles. 


Intake manifold and intake valve cleaning alternatives to walnut blasting

There are really three ways to clean your intake manifold and your intake valves. While walnut blasting is the most efficient, these other ways do work if you don't have access to the tools. These three methods are:

  • Manually scraping the intake valves using tool picks or using the "zip-tie method" (demonstrated in the video below).
  • Using LIQUI MOLY valve cleaner solution.
  • Walnut shell blasting using special attachments for a media blaster.

If you're wondering if blasting walnut shells against your intake valves or scraping a tool pick against them is safe, you should know that it completely is. These are the most effective and safest way to remove carbon deposits, and this is what the dealer does when you bring your car in for routine cleaning.


Guide to walnut blasting the intake manifold and valves of carbon 

In the DIY below, Aaron Davis shows us how to walnut blast and clean the intake valves of the detrimental carbon buildup on his 2016 Volkswagen GTI. While this DIY is directed toward VW owners, the process is similar on most makes/models of cars. Removing components to get to your intake manifold will be different, but the process of removing carbon deposits will essentially be the same. 


Volkswagen Models and Years Applicable:

This guide applies directly to these Volkswagen models:

  • 2015-2018 MK7 Volkswagen GTI
  • 2018 Volkswagen Atlas

While this guide follows the two models above, cleaning intake valves of carbon applies to all direct-injected cars, and the process is basically the same. The 034Motorsport tool used in this guide works on this list of vehicles:

  • 2006-2019 Volkswagen Jetta
  • 2008-2018 Volkswagen GTI
  • 2009-2017 Volkswagen CC
  • 2012-2018 Volkswagen Beetle
  • 2006-2018 Volkswagen Passat
  • 2015-2018 Volkswagen Golf
  • 2007-2016 Volkswagen Eos
  • 2015-2018 Volkswagen Golf SportWagen
  • 2015-2018 Volkswagen Golf R
  • 2017-2018 Volkswagen Golf Alltrack
  • 2009-2018 Volkswagen Tiguan
  • 2006-2018 Audi A3 & S3
  • 2005-2018 Audi A4 & S4
  • 2008-2018 Audi A5 & S5
  • 2005-2012 Audi A6 & S6
  • 2012-2017 Audi A7 & S7
  • 2011-2018 Audi A8 & S8
  • 2010-2018 Audi Allroad
  • 2012-2018 Audi Q3
  • 2009-2018 Audi Q5
  • 2008-2018 Audi TT


Tools required to clean MK7 VW GTI intake valves:


Steps required to begin cleaning MK7 VW GTI intake valves:

Step 1: Remove the Intake Manifold

The first step to cleaning your intake valves is to gain access to them by removing the intake manifold. Since removing the intake manifold is a fairly involved multi-step process, use this guide as a reference:


Step 2: Remove the Coil Packs

The next major parts that need to be removed are the coil packs. To do so, start by removing the nuts and studs using a 10mm socket and either a thin 10mm wrench or needle-nose pliers. 


Once the first nut is removed, you can pop the ground wires off. 


Once the ground wires are removed, you can use your 10mm socket to remove the 10mm studs that fasten the coil pack down.


Once those are completely removed, you can use your tool pick to disconnect the wiring from the coil packs themselves.


Now you can fully remove the coil packs from the spark plug wells. This is done most easily when the engine is up to operating temperature. Sometimes these can be stubborn, but you should be able to remove them just by pulling up on them and wiggling back and forth.



Step 3: Remove the Spark Plugs

You want to remove the spark plugs for a couple of different reasons. First off, by removing them, it is easier to turn the engine over. You need to turn the engine over so that the valves are at top-dead-center (TDC) when cleaning each of the valves. This ensures that the valves are closed and prevent any debris from falling inside the combustion chamber. 

The second reason the spark plugs need to come out is so that you can tell when the engine is at TDC. That will be explained in the next step. 

To remove the spark plugs, use a 5/8" spark plug socket on an extension. 



Step 4: Ensure the valves are closed

As mentioned in the last step, you want to make sure that the valves to be cleaned are closed. This just prevents carbon deposits and debris from falling inside the combustion chambers. To do so, use a long-reach screwdriver inserted into the spark plug hole. Turn the engine over by hand using a 24mm multi-point socket until the screwdriver moves upward until it doesn't anymore. This will indicate that the engine is at TDC for those valves. 

You should be able to visually inspect the valves and confirm that they are closed at this point. 




At this point, you're ready to begin cleaning your intake valves. When you complete one pair of valves, you will want to repeat this step for each cylinder. 


How to clean your intake valves by walnut blasting

Step 1: Ensure your intake valves are closed

Have you realized that this is important yet? Just take a quick peek inside your intake ports and make sure that the valves are completely closed.



Step 2: Setup and fill your media blaster

This step will entirely depend on the model of the media blaster you purchase. The one we're using is one of the cheapest on the market and was purchased at Harbor Freight. You want to use finely crushed walnut shells that you can purchase from either Amazon or Harbor Freight. 

Once filled up, you need to connect it to a sufficient compressed-air supply. 



Step 3: Blast the intake valves

At this point, you will want to use a specialized intake blasting adapter. Aaron demonstrates the process using O34Motorsport's adapter for Volkswagen and Audi. It helps to have an extra set of hands to hold the adapter steady for this part of the process. 


First, you want to attach your shop vacuum to the large port on the adapter and turn the vacuum on. This is to suck up all of the debris and walnut shells so that they don't go everywhere and get inside the combustion chambers. 


Next, you want to put the blasting nozzle inside the adapter and down inside the intake port. Open the valve and begin blasting the valves. Move the nozzle around thoroughly to ensure that you hit all of the surfaces. 



Step 4: Stop blasting and inspect

You will want to occasionally stop and inspect how clean the valves are and if you need to continue or reach for different areas. The two photos below demonstrate a dirty valve and a clean valve. 



Once your valves are cleaned for that cylinder, you can move onto the next one, repeating the steps above for each.


Step 5: Dry Crank Your Engine

Before reinstalling your coil packs and spark plugs, you need to dry-crank your engine. This ensures that you have proper fuel and oil pressure, as well as helps clean any remaining debris out of the intake ports.


Step 6: Reverse Steps and Reassemble

Once complete, you now just need to reverse all of the steps above, including the DIY link in the first step, and put your car back together. If you're having trouble reversing the steps or have lost your place, Aaron goes through the reassembly process in full in the video.


How to clean intake valves by manual scraping:

Step 1: Ensure intake valves are closed

It is important that your intake valves are completely closed. So the first step of any of these methods is to double-check and visually inspect that they are actually closed.


Step 2: Manually scrape valves

Using tool picks or whatever sharp skinny objects you have, reach down inside each intake port and just begin scraping. This is a tedious process, but it should knock most of the heavy carbon deposits loose. 

You can use this process to clean your intake valves completely, or you can use it as a first step before doing a full walnut blasting (which we have the process for below). 



Step 3: Vacuum up loose deposits

Using your shop vacuum, thoroughly vacuum out the intake ports. You do not want any of this debris falling inside your combustion chambers. 



How to clean your intake valves using LIQUI MOLY Valve Clean:

Step 1: Ensure your intake valves are closed

Again, it is extremely important your valves are completely closed. Just do another quick inspection to ensure that they are. This method will not be effective if they are open in the slightest.



Step 2: Pour LIQUI MOLY Valve Clean into the intake port

While this image doesn't demonstrate it well, you want to fill the intake port with LIQUI MOLY Valve Clean completely. Leave it there for ten minutes or so; that way, the product can break down the deposits.



Step 3: Manually scrape intake valves

The same as without using the LIQUI MOLY product, you now need to scrape the deposits off of the valves. Now that the deposits have softened and broken down, you can do this using tool picks or even a clever tool like a bundle of cable ties strapped together.



Step 4: Suck the liquid out of the intake port

Using some sort of fluid transfer pump, suck the remainder of the liquid out of the intake port. As an added safety measure, you can hit it with the vacuum afterward. 


That's it! You're done and can now enjoy your car once again with peace of mind. This DIY did involve quite a few steps, but as long as you follow along and reference this guide or the video, it should have gone together painlessly. If you're interested in more DIYs for your Volkswagen, you can visit or subscribe to our YouTube channel. 

author image
Written by :
Evan Madore

Writer/Editor at FCP Euro and owner of a daily R53 MINI Cooper, a track-built R53 MINI, and a 1997 Dakar Yellow E36 M3 Sedan. ••• Instagram: @evan.madore

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