So went ahead and tackled the spark plugs the other day and thought I’d share some of the things I came across. First of all if anyone has a v10 ex over 100k and hasn’t done plugs yet DO THEM! I have 116k on mine and was overdue for spark plugs just haven’t had time to do them. I got new cop boots and springs and replaced the plugs with the original motorcraft plugs. I also cleaned the MAF and throttle body while I was at it. The scariest thing I came across was on the very back cylinder on passenger side where it’s a pain in the *** to get to the spark plug was so loose I could unthread it by hand. So I’m glad I changed the plugs when I did cause that could have been bad. But here are some pics of the condition of the stock plugs and how worn they were.



All the plugs looked like this some worse than others.


Not one plug was still tapped under .060


Hopefully ill see better fuel mileage now. Before I was lucky to to get 10 mpg. my last fill up I got 332 miles on full tank.

 

I had the #3 plug blow out at 108k just before I was going to change them, bought the car with 104k.
All the passenger side plugs were a tad loose when I checked them before removal compared to the driver's side.
There are several people here that change plugs & boots at 50k and torque them to 20-28 ft/lbs.
The OEM plugs were put in with 15-17 ft/lbs.
The issue with loose plugs is not just the 6.8L, all the Tritons 4.8L & 5.4L are susceptible, too.

 

I’m lucky that didn’t happened to me. I thought I didn’t need to worry so much about plugs blowing out cause mines an 05 with the more threads on the heads then the earlier model excursions with only 3 threads holding them in. I guess if it was a early model it probably would have blown out. It’s funny though cause I also have a 00 excursion and never had any issues with the plugs when I changed them and since I’ve changed them. My older one with 200k miles seems to have a lot more power than my newer one with 116k miles as well which I still don’t understand why.

 

I changed my '05 plugs at 107k miles, gaps were all between .064 and .072 but they were all still tight, it did start more easily with the new plugs and felt a bit snappier accelerating and I got my best yet towing mileage of 9.5 MPG on the first trip with the new plugs.
Are the gear ratios the same between your 2 EXs? If the '00 has 4.30 vs 3.73 in the '05 that would explain the performance differences.

 

Yeah both gear ratios are 3.73 the only thing different on my 00 is that it has a k&n cold air intake and the less restrictive down pipe which I’m thinking about swapping both of those to my 05 to see what it does. My 05 also has 5 star tuning but still doesn’t compare to my 00. I’m actually able to do a burnout on my 00 the only thing I can think is maybe the previous owner/s did something to the engine.