Sounds EXACTLY like what my truck was doing. There's no telling how long you'll have to put up with this issue before it gets bad enough to throw a code. It bugged me enough that I just decided to preemptively replace all the coils and plugs (it was probably about time on a 10 year old truck anyway). A set of 8 lifetime warranty coils with 8 Motorcraft plugs only cost me $140 on Ebay. It took me about 3-4 hours to do the job, taking my time on a lazy afternoon. I probably could have got it done in 2-3 hours if I was in a rush. The problem was solved and the truck has been running better than ever.

 

Roger that warhammer. You have a link to the ones you used? And they've done well for you? I'm just gun shy as it seems everyone always says motor craft or bust. However, with a lifetime warranty, and the huge price differential I'm definitely interested.

 

It's been about 2 years since I replaced them, and everything is still great. The plugs are genuine Motorcraft. There just seems to be too much evidence that they are the best for our trucks to take a chance on anything else. The coils are aftermarket, but my research pretty much turned up that a coil is a coil is a coil... Here's a link to the guys I bought from: http://www.ebay.com/itm/SET-8-IGNITION-COIL-DG508-SET-8-SPARK-PLUG-SP479-/180811324837?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item2a1931dda5 I have to apologize for misquoting the price... The set costs $104, not $140.