Rough idle/misfire when cold then ok after drive it for 5 minutes

[hwydave]

Having an odd issue with my 2009 V6 (165k miles): The truck has rough idle when cold, and I sense some misfiring. The roughness goes away after I drive the truck for a few minutes to get to the normal operation temperture. The engine runs fine during the journey until I park the truck for a while and engine coold down and the misfire start again. I replaced the spark plugs and wires (all Motorcraft), and the misfiring still exists, but just not as rough as before. No CEL nor code. The tachometer dial is pretty steady (not jumping up and down). Any suggestion on where to investigate next? Thanks!

 

[Fbird]

Keep an eye on your radiator fluid level. Mine is/was seeping fluid into #4 hole, so started rough...burn off the fluid and run fine. 2 hrs later starts fine. wait 6-8 hrs and it started rough misfiring. Plugs had been changed about 10k earlier???? When trying to get to the plugs i tore up a plug wire so did them. Plug looked good (i had a code for #4 misfire), next up put on a coil pack. NOPE. Also notice very slight loss in antifreeze??? Let it sit over night removed #4 plug looked in with my borescope and YUP green fluid, confirmed by disableing igniition and using a paper towel spinned it over. YUP antifreeze. = HEADGASKET time. Currently all is well as I used some K-SEAL. I am NOT a chemical fix it guy but for my problem on this application it has resolved that issue. (6 months now as a daily driver)