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Family Owned: 30+ Years, Same Location and Ownership.

Nationwide Service Warranty.

Gainesville's first AAA Approved Auto Repair.


Carrsmith provides intake valve de-carbonization repairs for all import and domestic vehicles. Import: Acura Audi BMW Honda Infiniti Jaguar Land Rover Lexus Mazda Mini Mercedes Benz Nissan Porsche Toyota Saab Subaru Volkswagen Volvo. Domestic: Buick Cadillac Chevrolet Chrysler Dodge Ford Jeep GMC Lincoln.



Mercedes 300SL                       Volkswagen Type III

Carbon build-up on intake valves and fuel injector nozzles.

from the Carrsmith Service Department

My engine has a slight miss at idle and gets poor fuel mileage but the Check Engine Light  is not on. What could be causing this?

Carbon build-ups: You may have a build-up of carbon on your intake valves. When the spark plug fires in the engine's combustion chamber, it ignites a very precise mixture of atomized fuel from your gas tank and clean air that has passed through your air filter. Engine temperatures in the combustion chamber are in the range of 2,000 Fahrenheit. Carbon is a normal byproduct of the combustion process. The carbon tends to build up on the coolest area of the chamber, which is where the fresh air and cool gasoline are mixing and passing over the intake valve on their way into the combustion chamber. This carbon can get pretty thick. I've seen it up to a 1/2 inch thick on the backside of every intake valve on a set of cylinder heads from a single engine. This carbon absorbs fuel meant to be burned in the engine- causing it to be wasted, and it can block the openings of fuel injectors, inhibiting fuel delivery. Both of these problems can cause a rough running engine with no Check Engine Light.

Fuel Injection: In 1886 Karl Benz, who in 1926 partnered with Gottlieb Daimler to form the Daimler-Benz AG, received the first patent for a gasoline fuel powered car using a carburetor. It would be 68 years from inception before the passenger car would use fuel injection. 

Prior to 1954 all mass produced passenger cars used a primitive device called a carburetor to mix the fuel with the air going into the engine. The gasoline has to be atomized and mixed with air in order to burn. DO NOT TRY THIS but, I once saw a demonstration where someone dropped a lit match into a pail of gasoline and the match went out. He had let the gasoline sit for a little while before putting the match in so the fumes (gasoline particles that had mixed with air when the gasoline was poured into the bucket) could dissipate, otherwise the match probably would have lit the gasoline on fire. Carburetors were the original way of mixing gasoline with air so the engine could run. However, they were crude compared to what we have today and gave the engine much more fuel than it needed to run economically and efficiently. But, 20 years before smog, and with gasoline at 21 a gallon- who cared? Carburetors were used well past the advent of fuel injection. The last carbureted car produced for the U.S. market was the 1991 Ford Crown Victoria. 

The first fuel injected passenger car was the 1954 Mercedes Benz 300SL gull-wing. The retail price new was $7,300. That's a hefty price compared to a typical "grocery-getter" of the time, like the Nash Metropolitan at $1,673, or the Rambler Country Club at $1550. The fuel injection system in the 300SL was a fully mechanical system - pretty "dirty" by today's emission and fuel efficiency standards. It wasn't until over 40 years ago, in 1968, that Volkswagen produced a car called the Type III with a Bosch designed electronic fuel injection system. This system was very similar to the fuel injections systems used today as nearly all modern fuel injections systems are based on that system. Compared to the old carbureted cars and the original fuel injected cars, modern fuel injection systems are extremely miserly in their metering of fuel. So, they cannot afford for any fuel to be absorbed by carbon build-ups.

What Carbon Does: Carbon soaks up the fuel just like the charcoal briquettes in your barbeque grill soak up the barbeque fluid. You may have noticed, a few seconds after you spray on the fluid, the briquettes look dry again. This is just what happens in your combustion chamber. As the air/fuel mixture passes over the build-up of carbon on the back of the intake valve, fuel particles are absorbed that were intended to pass into the combustion chamber to be ignited by the spark plug. So, you have a very sophisticated fuel system, measuring out very precise amounts of fuel- exactly what you need based on your current operating conditions. Unfortunately, this metering system does not have a way to detect the carbon build-up on the valves, let alone account for the fuel loss there, in order to keep your engine running smoothly. And, it won't either. Because that would not be an efficient use of fuel.

What You Can Do to Solve the Problem: Get a fuel injection and combustion chamber de-carbonization service.  Call Carrsmith today at 352-378-7830.

We look forward to talking to you soon!

Schedule online now   , or call us at 352-378-7830 to schedule for your combustion chamber de-carbonization service, or any needed maintenance or repair. Shop hours are 8-5 Monday through Friday.