I have an annoying intermittent problem with my #3 ignition coil. 2003 scab 4.6. I only use my truck 2-3 days a week and usually not consecutive days. Truck runs rough. I think it might be a moisture problem. Check engine light is on and error code points to #3 cylinder. Now if I drive the truck 3-4 days in a row problem goes away and check engine light goes off. Especially with this hot and humid summer or after a rainy day this problem is worse. I have replaced coil and used dilelectric grease and it solves the problem for a little while but it still comes back. I dont fiind antifreeze on the boot. I've searched the threads but can't find anything. Thanks for the help

 

Could have a plug going bad. I had the very same issue in my 02 5.4. Changed the coil, cleaned the butterfly and plenum on intake, it still spuddered. It wouldn't happen everyday, but it got worse. Finally changed out the plugs and the problem went away.

 

Plug was also changed

 

Change the ignition coil. There like $50. Had same problem with my 2000

 

He said he changed it

 

Opps didnt see that. But you can always get a bad one.