I've got one or two cylinders that will stop firing at will. It doesn't seem to matter if the car is cold or hot. I have two M3's, so I changed out the cap, rotor, plugs and plug wires. No change. I know it's getting fuel because the catalytic converter was glowing when I limped it home and you can smell it from the exhaust. It doesn't seem to have any reason. It will just stop firing like the flip of a switch. Once the cylinders quit firing they stay that way. It doesn't do it off and on. Any body out there ever had this happen? I'm afraid I'm going to have to get it towed to the shop.