Got a friend with a 2006 M45 that is giving her fits. It usually drives fine, but sometimes it loses a ton of power on the freeway (down to 40mph tops) or dies completely. She pulls over and restarts it, and it drives fine for awhile.

The dealer initially said it was bad catalytic converters and replaced them, but the stalling issued remained. The dealer has looked at the car a few more times and has no idea what the problem is. She's afraid to drive the car anymore, so it just sits.

Any ideas? MAF would be my guess, but you'd think the dealer would have checked it.

Anyone? Bueller? Bueller?

I had a similar problem and replaced a crank position sensor and its worked perfect since. I have an 03 however but the engine is the same.

Thanks, after digging through a bunch of forums it looks like those sensors are the most likely culprits.