2002 Montana *P0304*

[klee]

I am getting a P0304 code with a flashing engine light. I have switched coils around replaced plugs and wires and no difference still idleing rough and code p0304. I have noticed over the past couple of months the my exhaust has a wierd smell no rotten eggs and that where I park in the driveway there is black spot in the snow from tail pipe. Please help desperate!

P.S.

I had a complete head gasket job done a year and half ago.

Also I was parked idleing when it just started running rough.

 

[melsg5]

Cylinder 4 is misfiring, go through the list on this link

http://www.obd-codes.com/p0304