how to determine which coil pack is bad. on 1998 Ford F-150

i know one is bad but not sure which one ???

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2 answers 2 comments
Which engine?
5.4l
Replace all coils. You will be glad you did, if you plan to keep the truck! Scanner can find misfire, IF you want to replace just one.
I would strongly recommend a set of eight as well as goo with an OEM or high quality coil. You could try disconnecting them one at a time until you find the one that does not effect how it runs and know that is the failed one as well.