AdamPacheco

my friend just started having the same issues. i went over the entire electrical system and found that the wire harness connecting the stock sub the the amp has a fault, the amp wears down over time. you need to remove the bottom screw holding the rear passenger seatbelt on then the small sill in the trunk pops out with body clips followed by the entire trunk floor just lifts out.the entire rear side panel will now come off with some pulling just about 6 body clips holding it in place. the sub box is held in place by 3 bolts one in the top one on the right side and one tucked away in the groove of the box on the right. the amp is on the back of the sub box and will need to be replaced. it is available direct from ford for around $160. good luck. and trust me i am 100% sure this is the problem. if you dont beleive me, pull the box out and wiggle the wire harness that goes from the amp into the back of the box while your stereo is running, it will cut in and out depending where you wiggle it. hope this helps!