Throttle body failures on the 5.4L 3v are more common than you think, luckily it will pop a code for the throttle body more often than not helping with diagnosis. Symptoms include start and dies, no start, a really rough idle, surging idle up and down more so in park, poor brake assist due to rpm fluctuation and wrench light on. If you find yourself in this situation I show you how to change the throttle body and reset the pcm to learn the new idle trims.