This is a reminder to pay attention to what your truck is trying to tell you.
I had developed a ever so slight rough idle when hot, it was worse when the a/c compressor was engaged.
So I started pulling the spark plugs and this is what I found.



The porcelain had cracked and a piece had fallen off around the ground electrode on this spark plug.

This is what the rest of the plugs looked like.



So I replaced the one bad spark plug and re-gapped the rest of them, and now she runs like this.

http://www.youtube.com/watch?v=LITROO7EqTA

 

Wow spike you need to cleen that engine bay up lol

I wish my truck ran that smooth

 

Oh you Disco I owners showing off again...
...that you have a place to set a glass of water on your engine.

That is smooooth though!!

 

I had a spark plug crack the porcelan body on my wife's Explorer. How old are your plugs? Had the gap changed much from when you installed them?

 

They have about 20,000 miles on them, they are AutoLite Iridiums.
When I put them in they were gapped around 0.35", when I just re-gapped them they were at 0.50".
That surprised me.
I put them all back to 0.35".
Even with the gap so far off my truck ran great but I had noticed a little power loss, so we will see if this remedies that next week when I drive her again.

 

That amount of change is surprising, other than wear. i wonder what else causes a gap to change like that?

 

I have no idea Danny, they are alittle worn but not to bad, the ground electrode is still good but there is a little "button" on the side wire thingy that is worn off.
If I remember right the Denso Iridiums that I used last time did not have those.
I wanted the Denso's again but they had to order them and I didnt want to wait so I went with the AutoLites (when I did this tune up 20k ago).
Next time I will wait.