The only thing that was screwed up with the head on my mother's van was a cracked exhaust valve. I replaced the whole head because she couldn't afford to be without a vehicle for more than a day or two, and I wasn't sure how badly the head was damaged until I got it all apart. I could have just replaced the valve and put the head back on.

It had a rough idle, and eventually started running rough at a constant throttle setting, but it always smoothed out if you gave it gas. Other than that, the van ran pretty good, and she ran it like that for about a year before I fixed it.

I'm not saying that the busted spark plug has definately caused a problem for you, but that piece didn't just dissappear. There's enough clearance for it to sit in the cylinder without hitting anything, but chances are that it was carried out with the charge on the exhaust stroke, and chances are it probably hit the valve.

 

As my Redneck comes through......Just take a shop vac and some small tubbing and vacume out the top of the cyl. Through the spark plug hole. Just make sure your shop vac doesnt have any thing in it when you do it, That way you can CSI the pieces pulled up from there. Had to do that one time while rebuilding a head..

 

Now that i think of it, i'm not sure if the electrode broke off or not, my dad thinks that half of it was bent back and it did not snap. I changed the wires and that did not fix it (didn't think it would). If it is the cap, is there any way i can test it before replacing it. I am bringing it to a garage tomorrow. It seems like it only misfires on idle, but i'm not sure.