What could be the problem?

[Pig Farmer]

Last night, my girlfriend's 650i started to run very rough. Felt like one or more of the cylinders were not firing. The check engine light came on, and sitting at a red light, I noticed a major cloud of unburnt gas coming from the exhaust. It was so bad, I was praying that nobody was smoking in the cars next to us. We limped home which was only a 1/4 mile away. After the car was shut down, it would not restart. However, gas fumes were visible when cranking the ignition. It seems pretty obvious that spark was not getting to one or more of the cylinders. It the old days, the first thing to check would be the distributor cap. With all the computers in today's modern cars, I wouldn't know where to begin. Does anyone know the most likely cause of this issue?

[Dackelone]

You need a scan tool to really know whats wrong, and then go from there.

[shodanusmc]

If it is under warranty, have it trucjed to the dealer.

[TEAM SLO]

Hope this all works out as best as it can be considering the situation.

[Pig Farmer]

Thanks guys. BMW sent a flat bed truck to pick up the car. Just waiting for the results of the diagnostics. Should be covered by the warranty.