How can I test to see if I have a bad coil?
Remove that specific ignition coil with the engine on and idling if your coil is working you will notice change such as a misfire and rough idle. If there is no change at all and is idling the same way regardless of the coil connected or not then your ignition coil is not working. Cheers
Ignition coils are tested by resistance, (Ω) readings. I do not know what all of them should be, but I do believe Auto Zone can check it for you.
Search Ford Expedition Questions
Ford Expedition Experts