My truck just recently started missing but only when warmed up.Runs fine until it reaches operating temp. Check Engine light is not on and has never been on!Drove it to work one day and was fine in the morning. when i went to drive home at end of day it started to miss when the truck came up to temp.
Truck has a miss only when warm on 2001 Ford F-150
Without the check engine light on, or codes stored in the engine module, this will require some hands on diagnosis. It may have diagnostic codes even though the light isn't on, so I would check that. Beyond that, you will want to connect a scan tool that can read live data and check to see where the fuel mixture readings are.