Strange smell and slight smoke from underneath after driving


I have a 2003 BMW 330XI that I bought used a couple of years ago. The car has shown no problems since that time except that sometimes slight blue smoke comes from underneath the engine and has a strange smell to it. It does not smell like burning oil or radiator fluid. My question is what might this be and how serious is it? This does not happen every time I drive the car, but it has been going on since I bought the car intermittent and I worry something is going to break.

I’d say something is broken. If it doesn’t smell like oil or antifreeze, then what does it smell like?

You probably have a leak. Whatever is leaking is probably leaving an occasional drip on something really hot like an exhaust manifold or pipe. You need to have someone find the leak and possibly fix it.

Possibly power steering fluid? That tends to cause a bluish smoke if it drips on the exhaust.

Sounds crazy, but I had a plastic grocery bag get caught on my exhaust a couple of different times - it stunk horribly until it burned off. Are many of these airborne on your commute?

I think frank438 is on to something. Burning plastic has a distinct odor. If it smells something like an old hair dryer it is probably electrical. I had a similar problem. For several months I would occasionally get a whiff of something that smelled like burning hair. It turned out to be the EGR solenoid melting. Look for stray wiring, relays or solenoids turning brown, maybe the radiator fan motor(s)