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