Ford EcoBoost Carbon Buildup – Symptoms & Fixes

Austin Parsons

Meet Austin

Austin holds a technical writing degree and has 5 years of experience working as a Technical Product Specialist at BMW. He is an avid car enthusiast who is constantly watching F1, consuming automotive content, racing on his simulator, and working on his Toyota’s and BMW’s. Austin’s technical writing skills, extensive automotive knowledge, and hands-on experience make him an excellent resource for our readers.

The Ford EcoBoost engine family is one of the most successful ranges of powertrains that Ford has ever created. Found in everything from the F-150 to the Ford GT, the direct-injected turbocharged engines have proven to be formidable, reliable, and powerful. Despite their solid reputation, EcoBoost engines suffer from a few common problems that have to do with the design of the engines themselves. One of the most common problems that affects almost every EcoBoost engine (besides the newest generation 2.7L and 3.5L engines) is carbon buildup. In this guide, we’ll talk about what causes carbon buildup on the Ford EcoBoost and what you can do to prevent it.


*This guide covers all EcoBoost engines that use direct injection only including all engines produced before 2017. The second generation 2.7L and 3.5L EcoBoost utilize direct and port injection meaning that they don’t suffer from carbon buildup like the earlier models.

What is Carbon Buildup?

Described simply, carbon buildup is the result of incomplete fuel combustion leaving behind a carbon residue that can get stuck to the intake valves, injector nozzles, cylinder walls, and piston heads. Oil blowby caused by the PCV system and valve seal weep contributes to the problem as well, worsening the buildup. While carbon buildup can occur in engines with different fuel delivery systems, it is far more common on engines with direct injection fueling like the EcoBoost engine family. 

Carbon buildup is a very hard and sticky substance that will essentially collect on any surface that incompletely burned fuel/ blowby oil lands on. As carbon collects in various parts of the engine, it can cause serious issues to not only the valves but even the pistons and other bottom-end components. 

What Causes Carbon Buildup on EcoBoost Engines?

As with most other engines that suffer from carbon buildup, the issue on the EcoBoost is caused by the use of direct injection. Direct injection is a staple feature of the EcoBoost engine series and for good reason. There are plenty of benefits to direct injection as opposed to port injection including the ability to inject fuel more accurately and efficiently while also allowing for better fuel atomization. Instead of a port injection system which introduces fuel behind the intake valves, direct injection introduces fuel directly into the combustion chamber. 

While that is the most efficient and effective way to fuel an engine, it also leads to a notable problem. With port injection, the fuel that is sprayed behind the intake valves by the injectors has a dual purpose of also cleaning off the intake valves from any buildup caused by incomplete fuel combustion. In that case, the valves themselves cannot accumulate any carbon buildup. However, with direct injection, there is no fuel actively cleaning the residue from the intake valves, leading carbon to build up on the valves over time.

One solution to the carbon buildup issue is by supplementing direct injection with a secondary port injection system. That is actually how Ford ended up solving the issue on the newest 2.7L and 3.5L EcoBoost engines. In that system, direct injection still works as normal, injecting fuel directly into the combustion chamber, while the port injection system introduces more fuel behind the intake valves, cleaning them while also providing more fuel flow for better performance.


  • Difficulty starting
  • Rough idle
  • Significantly reduced fuel economy
  • Engine misfires
  • Decreased engine performance under load

Carbon buildup on the EcoBoost is typically hard to diagnose unless the issue is pretty extreme. It generally takes around 40,000-60,000 miles for the carbon buildup to get bad enough for symptoms to manifest. Since it takes such a long time for the issue to get bad, it is likely that you won’t notice any symptoms at all for quite a while. 

When symptoms do appear, the most common warning signs are difficulty starting and a rough idle. When carbon collects on the back of intake valves, the buildup changes the way that air flows into the combustion chamber. That can affect the air/fuel ratio of the engine and take it out of OEM specifications. A hard time starting and a rough idle are two telltale signs of that.

Along the same lines, the buildup can also cause the engine to burn fuel incompletely, leading to an excess of fuel in the combustion chamber, causing the engine to run rich. In that case, the engine simply wastes the additional fuel, resulting in a significant decrease in fuel efficiency.

Since carbon collects on the back of the intake valves, it can cause the valve to not seat properly. That can have a severe effect on the air/fuel ratio, causing misfires, rough idle, and decreased engine performance under load. 

Can You Prevent EcoBoost Carbon Buildup?

So, now that you know what causes carbon buildup on the EcoBoost, the logical follow-up would be asking how to prevent it. While there isn’t a way to prevent carbon buildup entirely, there are certainly ways to slow it down by a significant degree. A couple of those solutions are using higher-quality fuels/oils, using fuel additives, installing an oil catch can, or even installing water/methanol injection. 

EcoBoost Oil Catch Can

One of the main things that you can do to reduce the amount of carbon buildup that collects on your EcoBoost’s intake valves is to make sure that you are using high-quality gasoline in your engine. Using higher-quality fuels and oils with a high-quality synthetic base will cause fewer contaminants in the blowby, reducing the chances that unburned fuel/oil leaves behind a hard residue. If you don’t have access to high-quality fuels, using a fuel addictive with polyether amine (PEA) can also help in reducing the risk of carbon buildup on EcoBoost engines.

Another popular option in the EcoBoost community is installing an oil catch can. The purpose of an oil catch can is pretty straightforward. They are designed to catch any contaminants that are rerouted to the intake from the PCV system, significantly reducing the amount of oil and other blowby from entering the combustion chamber. That is directly beneficial in reducing carbon buildup.

Finally, installing a water/methanol injection system can also reduce carbon buildup. In a way, a WMI system before the throttle body acts in a very similar way that Gen II EcoBoost engines use both a port injection and direct injection system. Water/methanol gets injected before the ports, which cleans them of contaminants.

How Do You Fix Carbon Buildup?

One carbon buildup gathers on the intake valves of your EcoBoost, it is pretty difficult to get it off. Since it is such a hard and sludgy substance, it doesn’t come off of the valves easily. However, there are a couple of ways to get it off including walnut blasting or scraping it off by hand. Either way, it is an in-depth procedure, as you have to remove the intake manifold to get access to the valves. 

One interesting but slightly problematic thing about removing carbon buildup is that Ford repair centers do not offer a solution if you take your car and truck in. While they recognize that it is an issue that can potentially cause drivability issues, they won’t actually clean the valves for you. That only leaves at-home solutions to carbon buildup, unless you want to pay for new valves entirely.

Walnut Blasting

Walnut blasting is by far the most popular and effective way to get rid of carbon buildup. That said, achieving good results with it is also pretty invasive and requires some specialty tools. Walnut blasting is exactly what it sounds like. During the process, you take an abrasive blaster, like the one linked here, and spray the affected valves with ground walnut shell media. The shells are coarse enough to remove the carbon buildup from the valves. Once you finish, you can simply vacuum up the shells. We made an entire video about walnut blasting that I’ll link below. While the video is about a direct-injection BMW, the process is identical to the EcoBoost.


Walnut blasting is the most effective and least time-intensive way to remove carbon buildup, but it can be costly. The media blaster and the walnut shells are relatively inexpensive and you can pick up both for around $150. However, you’ll also need an air compressor and a vacuum, which can add to that cost, if you already have the latter two items, walnut blasting is unquestionably the way to go.

Scraping The Valves

If you are looking to do the job yourself for the least amount of money, you can also invest in a set of picks that you can use to manually scrape the buildup off of the valves. There is no question that manually scraping the valves clean is a more time-consuming process than walnut blasting. It also won’t yield as good of results most of the time. However, it is a perfectly good option to get the majority of the buildup off of your valves for pennies on the dollar. 

As a side note, if you plan on using chemicals like valve cleaner while scraping, it is vital to choose a cleaner intended for use on turbocharged engines. There are reports of people using standard valve cleaner during this process which damaged their turbos in the long run leading to a far more expensive repair in the long run. Do your due diligence beforehand to prevent any unnecessary damage. 

EcoBoost Carbon Buildup Is a Once In a Blue Moon Issue

Despite how much you hear about carbon buildup on the forums and other EcoBoost outlets, the reality is that carbon buildup is only a notable issue after 50,000-60,000 miles. Even then, it is likely that your EcoBoost car/truck won’t show any serious symptoms that will warrant a response immediately. Every vehicle with a direct-injection-only fuel system experiences carbon buildup simply because the valves aren’t cleaned by fuel from a traditionally mounted injector.

If the carbon buildup does get truly extreme, you might notice performance issues like difficulty starting, rough idle, and hesitation under load in addition to poor fuel economy and misfires. While there are some more serious symptoms that can arise if the buildup gets seriously bad, those are fringe cases that are rarely seen. Carbon buildup can be reduced but not eliminated completely by using high-quality fuel and oil, installing an oil catch can, or installing a water/methanol injection system.

Unfortunately, Ford acknowledges that carbon buildup is an issue, but does not offer services to remove the buildup, leaving that to you. Walnut blasting or picking the buildup off of the valves manually are the two best options to get rid of carbon buildup on the EcoBoost engine. 

If you are interested in learning more about common EcoBoost problems, check out our 2.7L EcoBoost and 3.5L EcoBoost Common Problems Guide.

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One Comment

  1. I’m sorry, ford dropped the ball on this motor, still has a timing chain problem, 4k to fix just to have the same parts fail at around 100k miles, This motors good reputation only comes from the after market world, chain, Feisers, and oil pump and installed by an independent shop. Ford don’t take credit for something you didn’t do, still fixing your mistakes

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