Do I need to clean engine carbon?

A popular auto repair service up sell when you go in for an oil change would be cleaning carbon deposits from the engine. Sometimes they want to remove carbon from the throttle body or the throttle plates and usually make claims about improved idle or fuel economy.

Picture of throttle body service

In other cases they talk about cleaning deposits from the cylinder which is a much different process than removing it from the TBI air inlet. The throttle body service in my opinion has become a much more common auto repair up sell then cleaning cylinders and Pistons.

Again this is just my opinion but I believe there is a time and place for throttle body services. Chances are you would be asking for one if you really needed it, instead of being up sold the service during a scheduled oil change. For one thing the engine control module is capable of compensating for some deposits.

When the throttle plates or throttle body and idle air control motor become overwhelmingly covered with carbon the driver will usually complain about a rough engine idle, possibly a stalling condition or even a hunting or unstable engine idle. If your vehicle is idling fine and not having any problems you may want to consider a second opinion.

Cleaning carbon from the cylinder

Picture of engine pistons

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A buildup of carbon on the top of the piston or in the combustion chamber can also cause a unique set of engine running problems. When the carbon deposits build up to the point where the driver may notice something, one of the most common symptoms is pre-ignition which some people would call engine ping.

Removing carbon from the top of the piston is surprisingly harder than you would think. Many times I have seen mechanics try many methods such as different kinds of chemical additives or even squirting a water mist in the air intake to steam clean the chamber.

Water injection is effective at reducing carbon but before it is built up on top of the piston to the point where it is causing a problem. There are several ways to remove or at least reduce these carbon deposits. Yes in my opinion once again the best way is to disassemble the engine and physically remove the carbon with a scraper or a wire wheel.

Probably the most common method would be to add some kind of chemical to the fuel. Some of these work better than others but all of them work very slowly at reducing these carbon deposits which may not be helpful if you are experiencing a problem like engine ping.

Picture of clean engine

Another method that I have seen used which is not as common as it used to be is what they called a carbon blaster. This is pretty much like sandblasting the top of the piston but not with sand which would certainly destroy the engine. Instead they use compressed air to force crushed walnut shells into the combustion chamber.

These shells collide with the top of the piston and all areas of the combustion chamber without removing the cylinder heads. It does an amazing job at removing the carbon deposits. The problem is finding a repair center that really has one. The set up of one of these things is still labor intensive but also very interesting.

In most cases to use a carbon blaster the intake manifold and sparkplugs are removed. On some engines the injector can be removed instead of taking off the whole intake manifold. The output hose of the carbon blaster is attached to a cylinders intake port or inserted into the fuel injector hole.

The extraction hoses from the carbon blaster are inserted into the sparkplug bore which allows the walnut shell particles to be removed from the piston and combustion chamber area without getting down into the crankcase.

Carbon is a byproduct of combustion. Today’s engines run much more efficiently than the carbureted models years ago. Add to that the improved fuel blending that contains less impurities and today’s engines produce less carbon than ever before. It may still at some point be necessary for you to take action against the carbon deposits in your engine but remember that when this is necessary they are usually accompanied by noticeable symptoms.

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