At about 32k my xf started to do the check-engine light / stall out or near stall at some stoplights, but not every time. Took it in for an oil change and to have it checked out. Service tech said bad O2 sensor and wanted over $450 to fix it. Did some serious searching for the part online and just about paid $85 for one to change myself.

Now for the funny part, I had to take it back in because the tire pressure sensor light wouldn't shut off. They must have done a few resets because once they gave it back to me, no more check engine light and I haven't had it stall. She now has 58k and not a hint of any problems.

My suggestion - take it back and have the tech reset the ecm. Something is out of tolerance with the O2 sensor.