Carbon Build-Up And Cold Start Misfires on 2.0T TSI

There are few things worse than cold start misfires when you start up your engine in the morning. Carbon build-up and sludge that has built up over the years can cause significant problems or even failures in the engine of your VW or Audi 2.0T TSI. Several factors cause these cold start misfires. These problems could all be because of carbon build-up on the intake valve of your Audi or VW. However, there is an efficient process of cleaning these valves and restoring your smooth idle in the morning and having the bonus of increased power and fuel economy.

Why Does Carbon Build Up On Intake Valves On The 2.0T TSI? 

Most fuel companies like Shell, Chevron, and others blend a detergent into their high-quality fuel. The design of the cleanser works to clean out carbon build-up on the valves of the engine. However, the soap is only useful on port injection engines. Port injection engines spray fuel directly into the intake tract. Engines like the 2.0T TSI are direct injection engines, which means that they inject the fuel directly into the cylinder at the point of ignition (hence, the name direct injection). The detergents never are allowed to touch the intake valves, and this causes carbon to build up extensively.

carbon buildup on a mk6 gti

Why is Carbon Cleaning Important? 

Carbon build-up can wear your car down quickly. You may feel that your engine is stalling or slow to react in cold weather. Also, vibrations, noises, and roughness of the engine can all be explained by the carbon build-up on the intake valves of the engine in your Audi or VW with a 2.0T TSI. These types of symptoms will usually start to show themselves around 50k miles on the car. The carbon accumulates as a normal part of combustion but can be exacerbated by extended oil service intervals, short-trip driving that doesn’t get the car up to operating temperature, failures in the crankcase ventilation system, and even prolonged periods of low RPM driving (have fun with your car and take it to redline sometimes. Sometimes called the Italian tune-up!). Some of these causes are very difficult to avoid so an occasional cleaning as part of a maintenance plan will keep your engine running smoothly.

How to Clean The Carbon From The 2.0T TSI 

There are several ways to clean out the carbon from the intake valves on your Audi or VW 2.0T TSI. You will learn the best ways to clean intake valves and why access to the valves is important to properly remove the carbon deposits. Remember, the carbon build-up will look black and chunky. If they are clean, you may have other problems with the engine that need to be diagnosed by a certified auto technician. You can refer to our other article on how to inspect for carbon build-up here, or obviously, we can help you with that at Alex’s Autohaus. Three ways to clean carbon build-up from the intake valves on a 2.0T TSI are to blast the valves with a rough material like walnut shells, complete a valve job, or complete a chemical cleaning of the intake system. Now, let’s take a look at each of these carbon cleaning jobs and discuss their merits.

Blasting With Rough Walnut Shell Material To Clean Intake Valves On A 2.0T TSI

Media blasting away carbon build-up with rough materials, such as walnut shells, is the best way to reduce carbon build-up and limit cold start misfires. The steps that mechanics use to do this procedure are relatively straightforward. This is one of the best ways to remove carbon build-up in the intake valve of your 2.0T TSI due to being relatively cost-effective and completing a thorough cleaning of the valves

How Does Walnut Blasting Work? 

Walnut blasting your intake valves clean of carbon build-up is a great way to clean this component of your engine. Crushed walnut shells clear intake valves with something like an air pressure gun. We use special attachments to vacuum up the shells and make a nice and tidy cleanup job. Walnut shells are used because they are abrasive enough to remove the carbon deposits, but not so abrasive that they damage the aluminum components in the cylinder head.

Chemical Cleaning of The Intake System For A 2.0T TSI

One option in the past was a chemical cleaning put into the fuel system. However, for a direct-injected engine, these are worthless. 

We have tested almost every chemical cleaner out there from BG, Justice Brothers, Lucas, miscellaneous chemical products from the dealers, and many others. It doesn’t matter what the can says; independent testing has shown that a direct-injected engine with accumulated carbon deposits always remains stuck on the valve. We have independently borescoped and removed intake manifolds to verify this. If you recall how a direct-injected engine works you will understand why. The fuel is sprayed at the point of the injection inside the cylinder. All of these magical chemicals are just burned off and never touch the valves. Our best advice is to ignore these claims and when the time comes do a proper walnut media shell blasting of the valves. The only time we would recommend using a chemical is if the intake manifold is removed and the chemical is used to manually scrape the carbon deposits off. 

However, we don’t do this because frankly it just takes too long and we aren’t too keen on bending over an engine long enough to scrub the valves clean with a brush if we can use a tool to do the job properly and efficiently…which means cheaper for the consumer.

Valve Job

The method of last resort is performing a cylinder head job on the engine. This involves removing the cylinder head and disassembling the head to clean it. This is typically only done if the carbon build-up is so bad that it causes a valve to stick open or burn a valve due to a hot spot. Generally, if you are paying attention to your vehicle you will address poor running conditions before they get this far. Of course, there are rare exceptions when a piece of carbon breaks off and gets stuck before any noticeable symptoms occur. Although a carbon cleaning as part of a normal maintenance plan mitigates this possibility. The key takeaway here is to maintain and address issues early to save on the high cost of performing a cylinder head job.

What Is the Best Way to Clean Carbon Build Up?

The best way to clean your 2.0T TSI or FSI motor is walnut shell blasting, hands down. Chemical cleaning is wasting money on an ineffective solution and cylinder head jobs are too expensive as part of a normal maintenance plan. 

When in doubt give us a call at Alex’s Autohaus and we can discuss your situation and recommend your best course of action for your vehicle.


Carbon build-up can hamper the performance of any engine. Don’t let this build-up result in misfires causing check engine lights, loss of power, or loss of fuel economy. Once you have the carbon removed from your intake valves, you should notice an immediate increase in the performance and fuel economy of your vehicle. Taking the time to address carbon build-up can make your car run years younger!

Alex’s Autohaus is here to assist you in resolving these issues and we would love the opportunity to discuss them with you! Give us a call or contact us online today!

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