My buddy's 4.9 will crank and warm up fine, run about 10 miles then die. He says sometimes it will fire back up and run fine, sometimes it won't. He's replaced simple stuff like the fuel pump, plugs, wires, checked distributor. Do these trucks have a crankshaft position sensor? The guy at the auto parts store told him to replace this, but we couldn't find it in Haynes manual... Thanks