2012 Acura MDX Owner's Manual - Page 594

Emissions Controls The burning of gasoline in your vehicle's engine produces several byproducts. Some of these are carbon monoxide (CO), oxides of nitrogen (NOx), and hydrocarbons (HC). Gasoline evaporating from the tank also produces hydrocarbons. Controlling the production of NOx, CO, and HC is important to the environment. Under certain conditions of sunlight and climate, NOx and HC react to form photochemical ''smog.'' Carbon monoxide does not contribute to smog creation, but it is a poisonous gas. The Clean Air Act The United States Clean Air Actᤳ sets standards for automobile emissions. It also requires that automobile manufacturers explain to owners how their emissions controls work and what to do to maintain them. This section summarizes how the emissions controls work. Scheduled maintenance is on page 514. ᤳ In Canada, Acura vehicles comply with the Canadian emission requirements, as specified in an agreement with Environment Canada, at the time they are manufactured. Crankcase Emissions Control System Your vehicle has a positive crankcase ventilation system. This keeps gasses that build up in the engine's crankcase from going into the atmosphere. The positive crankcase ventilation valve routes them from the crankcase back to the intake manifold. They are then drawn into the engine and burned. Evaporative Emissions Control System As gasoline evaporates in the fuel tank, an evaporative emissions control canister filled with charcoal adsorbs the vapor. It is stored in this canister while the engine is off. After the engine is started and warmed up, the vapor is drawn into the engine and burned during driving. Technical Information CONTINUED 587