OK so I have a 2000 XJ 4.0 about 235,000 miles on it. It's started clicking real bad in the front near the timing cover and was taking longer to start than usual so I figured probably the timing chain. So I parked it. Pop open the timing chain cover to put the new chain on and notice the timing chain is not loose enough to be slapping the cover or anything else. So I look in the bottom and see this little broken piece of metal along with the rubber chain guide. What the heck does this broken piece go to? It's slightly curved with a groove on one side.

 

The piston broke. Broken skirts seemed a bit common in those at times.

 

My first thought was piston skirt but he found it in the timing chain cover, not the oil pan so it's not a piston skirt. OP, is it made of aluminum? It looks like part of a pulley.

 

Is the front (balancer) seal intact?