1999 Saturn SL2 Engine idling very rough

I was on my way to work this morning and my engine suddenly started running very rough. It sounds like one of the cylinders are not firing. I checked the spark plug wires and they are still on tight. No oil or water is leaking out of the engine externally. Is it possible that the timing chain slipped? The engine has a smell like burning gunpowder as long as I can keep it running. The service engine light came on enroute to work and then the engine began to have the problems described. What are some possible causes of these symptoms?

Thanks in advance,

Chip Armstrong