Engines work when gasoline enters a combustion chamber, where it's ignited by a spark plug to extract energy. The gasoline is sprayed in by fuel injectors, and the engine's efficiency depends on these injectors performing at their peak. This includes how clean they are.
"Carbon can clog the injectors and the spray pattern, and the efficiency of the fuel is impeded," says Al Manji, managing director of MOC Distributors of Canada, a provider of chemicals and induction service for cleaning injectors.
"Carbon is like a resistance substance in the car that makes it work harder," he says. "It's like clogged arteries where the car isn't 'breathing' or functioning as it should."
Carbon is a byproduct of fuel combustion, and over time it can build up on the injectors and on the back of the throttle plate. This can mean small quantities of unburned gasoline left in the combustion chamber, which reduces fuel efficiency.
Injectors have specific spray patterns to ensure fuel is sent to the optimum area within the combustion chamber for maximum efficiency. If the injector tip is clogged with carbon, "It's like taking the tip of a garden hose and putting your thumb over it," Manji says.
"Fuel doesn't go into the spray pattern that it should. It causes hot spots, it sometimes causes pooling of fuel, and the fuel ends up dripping out of the injectors instead of being sprayed out. Any time that spray pattern is inhibited in any way, the car ends up suffering downstream."
If the injectors get too clogged, the engine could misfire or even stall, Manji says. Computer-controlled engine management systems are very finely tuned and can be altered by carbon build-up, which in turn results in the engine running poorly.
Some engines use direct fuel injection, which sprays the fuel directly into the combustion chamber to be ignited by the spark plug.
"It's more efficient, but the spray patterns are much finer, the (fuel pressure) is much higher, and the need for a cleaner-running system is that much more important," Manji says. "If it's not running optimally, it can cause some serious issues in the system as well."
Jil McIntosh is a freelance writer who reports about cars for publications and on her website www.womanonwheels.ca This story originally appeared in Metro Canada.