My 04 developed a slight tapping sound and a miss. The tap and the miss would go away after a few miles. This happened twice a couple of days apart which made me think a valve was sticking or maybe an injector was trying to plug. The second time was like the first and it went away after a few miles. After it had set for 5 or 6 hours I tried to start it and it turn over slow 3 or 4 times like the batterys were weak then it fired and started running. At this point it sound like a van load of illegals were under the hood beating on the block with sledge hammers. I shut it off pronto. I started it again and it fired right up this time but with the same terrible noise. To me it sound like it had something on top of a piston. So I thought it must have drop a valve. The missing and the tapping should have been a clue as to what was about to happen. So I think the head needs to come off. Now I have the valve cover off and the rocker arms out but all the valves/springs/keeper/etc look ok. I pulled the injectors thinking maybe a tip had come off and they all look ok. I have heard about these injectors making big noise when they malfunction. Should I send them off and have them checked? Who should I send them to. I dont really want to pull the head without good reason. It doesn't seem likely that a valve came apart and everything stayed intact on the topside does it? Was the weak start due to fuel on top of the piston. Number six exhaust looks like it may have been wet although this happen a month ago and I am just now working on it so I cant say for sure. Anyway, I would appreciate any suggestion/experience/help. Thanks much dd