So in continuing my 2 for 2 streak of buying crappy cars with hidden problems, my car has a rod knock. When I bought it there was a very loud timing chain rattle. It was an easy fix- pull the valve cover and notice that the upper timing guide has broken off and is bouncing around in the timing cover . Of course I pulled the other one and unstuck the tensioners in the interest of doing things right. Unfortunately when I started it back up there was a much quieter rattling noise, one which goes away when you pull the #2 spark plug or fuel injector wire.

Is there anything else it could be? All I can think of is #1 rod knock, #2 bad exhaust leak on cyl #2 only, #3 spark plug wire arcing, #4 bad wrist pin or something else weird like that (?). I already eliminated the plug wire thing by swapping them around, and I'm 95% confident it's not an exhaust leak. It really sounds like it's coming from the block, though I couldn't isolate it anywhere with the screwdriver-ear trick.

If anybody has any suggestions let me know- I'd like to check everything before I buy another engine and tear this one down for a rebuild.