One problem related to ignition coils failure has been reported for the 1998 Ford F-150. The most recently reported issues are listed below.
My 1998 Ford f150 4x4 blew 3 coils within 3 months of each other, culminating with the ignition coil in August 2004. I contacted Ford and was told I was being put on a "recall list" in case others had complaints. When the coils blow, there is a horrible noise from the engine and an immediate loss of power due to the spark plug no longer igniting that cylinder for the engine to run off of. Luckily, I was able to pull over to the side of the road and call a wrecker without incident. All three coils were replaced and I still have receipts. I traded the vehicle in due to the numerous problems it began having.