Rough all the time
 

I have a 97 Expedition with a 5.4 engine and 89,000 miles. It is running rough at all speeds. The check engine light stays on and somtimes it flashes. I had the code read and it was a misfire in the #6 cylinder. The mechanic told me it was probaly the spark plug, so I changed them and nothing changed. I think it is probably the #6 injector but it could be the coil pack or ignition coil. Can anyone help me find out which one it is?

Rough all the time
 

It is almost certainly your coil pack. They cost about $45 from the dealer. It probably cracked because coolant was leaking from the heater hose above when the system is under pressure. Just slide the compression clamp back a bit and put a screw type clamp on by first unscrewing the clamp so that it can be slipped around the joint. The give-away to this scenario is that the plug should have rust around the bottom where the socket slips on. The rust is from the heater hose leak. The coil crack may or may not be visible - mine was.

Rough all the time
 

I agree with it being the coil pack. Many have had similar problems and found it to be the coil pack. Normally, it is some type of water damage, just like the above posting.

Jakegypsum // Ford fleet, soup to nuts.

Rough all the time