Strange sudden symptom

[Beamveh]

Wishing all the absolute best this new year! My 2009 328i has been always running like a clock -- went to its garage last night at her regular bed time after the typical nice smooth ride. But when I got in the car this afternoon, press start, and all of a sudden the engine is shaking, car shaking, confused RPM, exhaust seems stronger from one side than the other, exhaust odor also seemed different, etc. While cruising last night, I noticed the avg MPG reading 99.9 instead of the typical 24.5 -- I'm in DC metro. My question: Could this a misfire from a bad coil/plug? a bad fuel pump??? what is going on??? what could that be? Worried because this shake reminded me with my high-school motorcycle -- Honda 600 XL -- which did that same dance before it died. This car just turned 70,000 and has been pampered since birth! Thanks for all your help. Best, Roma

[CODES]

CEL on?
What code?
Could be many things including vacuum hose.

[cochise325]

Could very well be a bad coil. Have they ever been changed? You should make sure there is no oil in the spark plug wells. The oil can cause a short and therefore a misfire. The oil can leak from the valve cover gasket.

You should get a code reader and pull the codes. A vacuum leak can cause rough running.

[Critter7r]

At idle, the exhaust will only come from one pipe and not the other.

If there's no CEL, and it only happened once, chalk it up to a fluke.

[grabbat]

Most likely the smell is from unburnt fuel from a misfire, specially that it happened out of sudden. Is service engine on?