Just an update. I looked at all the sensor inputs from stone-cold this morning and found that the air inlet temp sensor is off by just over ten degrees. The ambient temp was 43-44F. The coolant sensors read within a degree or so of that, but the air inlet temp read 55F. The car was in the shade, so I don't think it was picking up any solar heating. Could this variation cause this symptom...Which was not as pronounced today as yesterday. The engine didn't die, but did it's usual 'stumbling' a bit as it crosses over from open to closed loop operation.

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2003 BMW E53 X5 4.4