Secondary Air Injection System: Description
WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2002 Mercury Sable, 2002 Mercury Mountaineer, 2002 Mercury Grand Marquis, 2002 Mercury Cougar, and 2002 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
The Secondary Air Injection (AIR) system controls emissions during first 20-120 seconds of engine operation by forcing air downstream into exhaust manifolds to oxidize hydrocarbons and carbon monoxide created by running rich at start up.