i just had the same problem 3days ago. Oil leaks and coolant leaks. Fixed both. I had my Coolant leak fixed, VCG, spark plugs and OFHG replaced. Got car back and rough idle. Felt like it wanted to stall and sporadic rpm not to mention, very rough start up especially on cold start up. Mech said it's a vacuum leak. During repair, one of the broken hoses got nudged and noticed vacuum plugs where starting to go bad also. Fixed the hoses and replaced the vacuum plug, now running smooth as ever at 650rpm.
Get a smoke test.

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2011 X5 35d 123,000 miles sport space gray/oyster

2005 X5 3.0i sport package Style 211
157,500 miles

2005 Chevy Avalanche Z66 BFG T/A Offroads