Secondary Air Injection (Air) System: Overview
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2006 Mercury Mountaineer, 2006 Mercury Monterey, 2006 Mercury Montego, 2006 Mercury Milan, and 2006 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.
The secondary AIR system controls emissions during the first few seconds of engine operation by forcing air downstream into the exhaust manifolds to oxidize the hydrocarbons and carbon monoxide created by running rich at start up.