I have done a search and I know the code my car is throwing is a Random misfire (PO300), but before I get to my question here is a bit of background leading to it.

List of problems:

- Axle back flang rusts and blows off. I take muffler off since I ordered a new Cat-back. During this time (I still havn't received my cat-back) the car develops a random misfire code, but doesn't loose any power.

- I figure this problem is due to spark plug, and with over 145,000 km's on the car I change my spark plugs.

- After changing plugs (NGK R Platinum plugs bought from Nissan Dealer) I accidently plug in harness for cylinder 2 into cylinder 4. I put everything back together and get a knock combined with mis-fires and what not. My buddy and I pull everything apart and put it back together again. Same thing.

I got frustrated and drove it home (about two blocks away). I pull everything apart and check the color of the plugs. Figure out the problem and motor runs fine.



NOW, the problem is my car is producing a random mis-fire code again and struggles with power above 3000rpm. Massive power loss in all gears and the only code I'm getting is P0300. I am also hearing a rattling from my exhaust. Any suggestions?


I'm possibly thinking it's the cat on my left bank that got plugged due to the mass amounts of fuel dumped into it, and then maybe the exhaust back pressure into the left bank is high-enough to bring the exhaust back into the cylinders and not allow complete combustion. Could I be right? Or wrong?

I apologize for the lengthy post, but I need to figure this out.


****EDIT****
car is 100% stock
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**update**
I also get some sort of a burning smell coming from the car when/if i give it. It's not plastic, no rotten egg (sulfur smell).

I also heard a hissing sound from one of the coil packs, but I pulled the plug and saw it was running rather lean (as oppose to rich which usually happens with malfunctioning coil packs).