welcome to CEG!
HERES YOUR PROBLEM! You are using the WRONG spark plugs, our engines dont like anything but Autolie Double Platnium and Motorcraft spark plugs. I got some Champion Double Platniums and my engine cracked the #2 cylender plug, replaced it with a set of Autolite's havent had a problem yet. How many miles are on your tour might I ask? and what engine do you have the Zetec 4 cylender or the Duratec 6 cylender?
