Recommended Procedure
WARNING: This page is about a different car, the 2008 Ford Pickup, 2008 Ford F550 Super Duty, 2008 Ford F450 Super Duty, and 2008 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Inspect the air cleaner inlet and ducting to make sure it is not blocked or collapsed. Inspect the air cleaner housing and filter for proper installation.
Inspect for any indication of water intrusion into air cleaner and filter.
If necessary, use DSL ENG Pressure Test Kit 014-00761 or equivalent to install a Magnehelic Gauge® on the port on the air cleaner and measure restriction at high idle.