True. It should idle rough from the start, unless it’s even dripping across all cylinders, which is unlikely.

Anytime I think about problems that show up after extended cold sitting, I think of fuel delivery. Especially since it seems to happen only after the cold of night time.

Fuel starvation for some reason? That would cause lean misfire and the computer to retard ignition to reduce detonation.

Failing return valve in the fuel tank that allows line pressure to drop after the pump shuts off, possibly causing short term initial starvation? Small Frozen glob of water in the fuel tank pickup? Cold causing low voltage to the fuel pump?

Please keep us posted on what you find.

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2005 X5 4.4i SterlingGrau, Sport Package, DSP
Build 3/12/2005