2000 Saturn SL1 No power, barely runs, clicking noise

2000 Saturn SL1
1.9 Liter, 4 Cyl, 16 valve, overhead cam
90,000
automatic
2 wheel drive

Overview of Details & what I have Looked at / Discovered so far:

Engine was running fine while driving then may have hear some noise (clang or a clicking) just before it died.
Engine stopped running while driving (stalled in traffic)
Engine started when I tried it the next day.
Engine runs extremely poor and rough, It barely runs as if only 3 cyl. Are working. Stalls at a stop, but will start right up after the stall.
Engine is clicking or clanging somewhat loud.
Clang/loud clicking seems to be coming from just below the cam shaft cover (top engine cover)
Noise sounds like something is loose & is rattling at a certain pace that speeds up with engine rev.
Noise seems to be located near cyl # 4
Removed cam shaft cover (top engine cover) no visibly damaged rockers, springs, or cam lobes. Knock seems to be deeper in engine, either in valve area or piston area, can't tell.
Checked visually / manually to see if any valves are pushed toward pistons (opened) while pistons are at top dead center. None are. This indicates to me that my timing chain either did not jump or did not jump very far.

Timing chain seems to be tight.
Ran the engine with cover off, no visible broken or sticking anything. Seems like springs ar ok but did not test them in any way.

Pistons, while moving crank by hand, seem to be moving ok.

Can't find markings on timing chain to check timing better (no silver or gold or black links can be found anywhere on chain). I did find markings on cam gears.

One interesting find that may or may not be related to entire problem: one evening I was running engine (it was dark out) I could see sparks around each spark plug boot at the coil and at the metal hold down plates at the plug wells, arching seemed to be everyehre I looked near the wires & metal. Even though I ohm'd them out and they were approx. 6, 7, 8, and 9 K ohms respectivly each.

Was thinking : engine could be running poorly due to bad wires or coil but the knock doesnt make sense unless there is a broken valve, or a piston rod or piston rod linkage that is loose or broken, or spun bearing. Anyone have any Ideas or seen this before? Or can suggest another check/test for me to try. I'm not sure if I should replace the wires & coil only to continue to have the problem or start taking off the oil pan or the head next. I would like to do the easiest procedure or pinpoint problem via someone who has seen this before.