Have you been seeing any coolant loss?

yes, but not much.. and i cant find where its going.

cooling system pressure test and compression check might want to check into these to get a better pic of motor condition

Well this sort of thing happened to me. But wasn't my XJ....thank goodness. It was in my geo metro. I was losing a very tiny amount of coolant. Was was happening was the head gasket was leaking coolant in my 1st cylinder. Seemed to onpy do it when I shut the car down. I say that because when I starts it up in the morning it smoked a tiny bit and after awhile it would stumble and run on only 2 of the 3 cylinders for a few seconds. Thought it was my dizzy. But nope. This happened for a few months....gradually getting worse. Then one day at work I drove to get gas and the whole time it ran like crappy and smoked....ended up hydrolocking the motor as I pulled in to ky parking spot. So a new head gasket went on that night and my plug looked just like yours. Worse actually. So you could have a very small leak in the head gasket. Not saying you do....just don't rule it out. I did....and ended up locking the motor up. Luckily no damage what so ever. New plugs and head gasket....among other things....and the car runs like a champ now. Hope this little story helps...

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Judging by the spark plug that cylinder is burning coolant. Id say possible cracked head. Does it misfire after sitting overnight?

Sometimes... but its not a constant thing. Wouldn't a cracked head make it lose some compression though?

Not always. It could just be a small crack into a water jacket that only opens up when the engine is hot. Usually leaking some antifreeze into the cylinder after sitting overnight.