5.4L (Eddie Bauer) will stall while driving 70mph on the highway. I can wait 2-10min and try the key again and it will run fine after that. This can happen once every 2-3months or at rare times 2x in one day. This can also happen while driving slowly through an intersection. Climate not an issue as it will happen in cold or hot weather. When it starts to stall it will futter a little. Feathering the gas pedal does not make a difference. I've taken it to a reputable FORD dealer and a good local one in town and they cannot find anything. Response - bring it back when it's not working. There are no error codes when this happens so it can't be tracked. I can hear the fuel pump engage when I first put the key in so I know it's getting the pressue it needs. I've replaced the alternator harness thinking there could have been a short which showed a wire burned, but the problem still exists. I've been told the IAC, TPS, coil packs and spark plugs could be causing the problem. To me it doesn't explain the sudden shotdown of the entire system when driving 70mph down the highway.
This one is hard to find do below immediately to determine if its fuel or spark problem
Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 away from ground-have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, Do you hear the fuel pump come On when you turn key on? If not check fuel pump fuse and fuel pump relay if okay-check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs, coil's resistances, cap and rotor, distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it and keep testing