No
Moisture will be the cause for an engine misfire. Depending on the year of the car will have a bearing on the solution. It could be that the plug wires are misfiring due to dampness.
Yes it can.
lack of fuel
There are several things that can cause your 2003 or Expedition to misfire. The most common cause is a plugged catalytic converter.
No it will not cause misfire.
Contaminated fuel could cause a misfire.
You can check the battery connector. Make sure they are not corroded; and see if there isn't any melting on it; sometimes it will startup but drive rough, make sure the the connection is tight. Also I think platinum spark plugs come standard on some Buicks, which have a very small electrode and a little gunk will cause them to misfire; I would swapped them for a set of old champion copper plus spark plugs and a new set of spark plug wires.
Yes.
It could.
A malfunctioning battery can't provide enough power to your ignition system when the motor is idling can cause sputtering. If there is not enough gas, that can cause your vehicle to sputter. If the spark plugs fail to fire will also cause your vehicle to sputter.
Yes. When you suspect it is clogged, replace it.