Glow Plugs
WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, 2012 Ford F450 Super Duty, and 2012 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The glow plugs are located in the cylinder heads and preheat the air inside the combustion chamber to improve cold engine starting.