Weird Rough running ka, please help!

[gthbryce]

I was driving to the local community college in my 92 240sx ka24de today when all of a sudden the engine started running really rough the tailpipe sounded like it was farting. To make a long story short the second cylinder was not firing so, I went and bought four new ngk spark plugs and replaced them. It did the same thing after i revved it once. SO i removed the cap and cleaned it. That seemed to help but i already had a new rotor so i went and bought a new cap. It ran better for like 20 minutes and then it started running rough again when idling and pops out the tailpipe a lot. My iavc is clean for sure thats not it, all four injectors work they are new and i also did the screwdriver test to make sure. I know for a fact that the timing chain is a little lose the car has 223k on it if this might have anything to do with it? I unbloted the distributor and moved it forward towards the radiator and it runs better but i put it back to where it normally is because i dont want to ruin the engine by running it lean or anything since i dont know what the problem is. On top of this the valve in the third cylinder leaks oil a little and my cat is problably ruined because the exhaust stinks and they dont like oil much do they?

So If anyone can tell me what the possible cause would be of the rough running engine let me know? Its more of a recent thing i have done a lot of work to this old ass engine and have drove 1700 miles from texas where i bought it to California where i live just fine and it hasn't acted up until now besides it leaking a little oil when i rev it relatively high and the exhaust smelling like shit.:ugh: I have a baby on the way this is my only car and im attached to it so i need it to run fine so i have reliable transportation. Thanks for any and all help.

p.s sorry that my story ended up being not so short. lol

[gthbryce]

i was driving home from my friends house tonight and i punched it down a street, then it went back to running on three cylinders and popping and bucking. it corrected itself and felt like it went back to four cylinders. And then something else to mention, after i bought my new spark plugs today i tested them and didn't see any sparks but what did happen was that i heard electricity arching somewhere else and at various times i saw it arching on the metal below the ignition coil. but when i started it, it seemed to be running on all four cylinders besides sounding really rough. could i be having a spark issue?