Wheels: Bob C. writes by e-mail “My 2004 Chevrolet Venture van is nearing 100,000 miles. I went to the dealer to find out if there is a preventative maintenance procedure to keep the car in good running condition. Among the suggestions was decarbonizing the combustion chambers. What is this procedure? The car runs fine except for a slight roughness at idle. Any other suggestions? Thanks.”  

Halderman: Thanks for writing. I would tend to agree that a decarbonization would help but not just the combustion chamber. Most machines (Motorvac is one brand name) that are used for this procedure send a cleaning solution through the fuel rail (part of the fuel system that supplies fuel to the injectors). It does not use the chemical through the fuel tank where it could cause problems with the fuel pump inside the tank. The cleaning solution contains gasoline and the engine is run for a while with the cleaner flowing through the fuel rail and the injectors. As a result, this cleans the fuel injectors as well as the intake tract and the backside of the intake valve where deposits form. Part of the machine also uses a sprayer attachment that forces some of the cleaner through the throttle body where it cleans the throttle plate, which is another place where deposits form. To me, this is a cost- effective way to improve vehicle performance and should improve the idle quality and make the engine operate smoother unless there is another fault with the engine or injection system.

Submit questions to jim@jameshalderman.com or follow him on Twitter @jameshalderman, or write to: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.