Crap I thought this was strictly an FX45 issue.

I moved the X5 out of the garage to clean the floor and then 15min. later returned it to the garage. The next day after starting the X5 there was a severe engine knock, a check engine light and the cabin filled with exhaust fumes. I let it idle, the engine light turned off and the knocking stopped with no problem since.

Not all FX45 owners had this experience and there was never a clear explanation for the knocking and fumes.

How about the X5 forum experts. I now know to allow the engine to warm up before shutting down but why should this be necessary?