2000 Hyundai Elantra cylinder 4 misfire

Hi.I have a problem with my 200 Hyundai elantra. About 2 days ago on my way home from work, my engine start to miss and function irregular. So I plugged in the ob2 and i've got the code:PO304 engine cylinder 4 misfire.I change the spark plugs and the engine still goes in 3 cylinders.I check if the spark plugs get juice from the coil. So I unplugged every wire from cyl. # 1, and the engine almost died on me, but I plugged the wire right back in the coil.I did the same with cyl. #3 and #2 and i've got the same result. Except with cyl.# 4. The flame -spark- was there but the engine didn't recognize the difference when I unplugged the wire from the coil or when I plugged back in the coil.
If you guys can give me any suggestions of what it my be the problem, I will appreciated. Thanks