My 03 XLT got a tune up two weeks ago for the first time at 110k. I
was a little intimidated by the spark plug issue and had been holding off. I had been missing intermittently for 2-3 years but not enough to be considered a problem. I wasn’t driving it very much but noted the gas mileage was gradually getting worse. Of course it ran fine a month ago when I completed a 1400 mile move back home, even giving me 20 mpg on a leg of I-10 in AZ - pretty good for a 5.4/4x4/3:73 with a pretty good load in the back. Fell off to 17 in the heartland. Anyway, it waited to get in my driveway before #1 coil decided to give out. I took it to the Ford dealer where I bought it new. Yeah, it was expensive but it runs a lot better now. The service manager said it would go thru a couple of tanks of gas before the computer caught up and I, still on my second tank. 1st after the tuneup gave me 11, all suburban city. 2nd seems to be better. Anyway, I’m hoping the plugs stay put in the heads and I can continue to enjoy this vehicle a while longer. I’ve driven a lot of cars over the years but really like this one cause it’s paid for and is mine!