Strange Starting Problem

[1stBMWTom]

Hi all,
I just purchased my first BMW about 6 weeks ago, a used 2006 X5 4.8is that had about 16,700 miles on it.

I've had a weird starting problem occur two times under similar conditions but never at any other time. On both occasions the problem happened after the vehicle had been on an incline or lifted up. Once was after driving up ramps to do an oil change, the other most recent time was after jacking up the rear to put on my winter wheels/tires.

The problem is as follows....when you first turn the ignition key and the engine starts, it barely catches and then barely stays running and idles very low. It almost sounds like it is running on/pinging/dieseling. It's a very disturbing metallic-like sound but is probably just due to the low idle of the engine. When you shut the engine off and try to restart, it has a very difficult time restarting. When it finally does you can definitely smell unburned gas from the exhaust.

This has only happened twice in 6 weeks and both times starting directly after having the vehicle on an incline. Any thoughts?

As an aside, I've been working on all sorts of cars/trucks for about 24 years. I also build and tune high performance engines, so I'm no stranger to working around vehicles. This one certainly seems odd though so I thought I might throw it out here to see if it has happened to anyone else.

Thank you in advance,
Tom