So, I did my timing belts recently (although the old ones ended up looking just fine, so I'm a little bitter), drove 2 1/2 hours without issue. Then, yesterday, I start up the car to go home from work, and it starts making this knocking sound. Crossed my fingers, drove half an hour home. Stalled once and seemed a little underpowered at first, but then evened out. Besides the sound, it drove fine.

 

Sounds like it's coming from the timing belts, so I ripped everything out again to find the driver's side belt looser than Charlie Sheen's morals. I'm surprised it ran at all. So, my first thought, the tensioner bolts must have come loose. Still felt tight, but I loosened 'em up again, and fiddled around with it trying to tighten up the belt again. Tensioner didn't feel like it moved at all, but something I did made the belt taught again. Started it up, noise is gone.

 

Now, what scares me is I have no idea why it came loose in the first place. The torque on those bolts isn't that much. I also found a good slice in the timing belt cover right above that tensioner (attached picture). I think I'm going to run without the covers for now and see how it holds up. What do you guys think?

i left my covers off you just dont need to run over anything like bags or anything that can get sucked in the belt an on the tensioner  if its loose  check the spring 

that's definitely a pulley rubbing into that timing belt and the cause of your noise.  is that on the top of the cover where the drivers side tensioner sits, looks like it if my reverse transpositional abilities are working?

 

are the bearings in the pulley good, loose, or how does it spin - tight or loose and free?   good job replacing your belts, EA timing belts aren't known to be wildly successful beyond they're 60k mileage interval. 

 

good idea to use the ebay timing belt kits and install all new pulleys, the originals are devoid of grease by now.

 

those timing tensioner bolts can strip - they aren't stripped are they?

 

if they're not tight it'll slap or move under load and you may not notice it at static conditions.

 

if they are the easy fix is to simply install a longer m8x1.25 bolt, it'll grab deeper unused threads.  best to chase the threads with a tap first to clean them all but if you don't have one the longer bolt will suffice as is.