Not this will help in your case but it worked for me in my chrysler cirrus turned out to be a poor/nonfunctioning EGR valve. I have herd of others having this problem on this forum too with the xf. Do a search for EGR valve.

EGR what it is...

EGR valves were introduced by car makers in the early 1970s as an effort to reduce the emissions created by an automobile's engine. Exhaust gas is recirculated into the combustion chambers, lowering the combustion temperature, helping to reduce pollutants. An EGR valve that fails to operate properly can alter the proper fuel and air mixture ratio of an engine causing poor performance*(missing)*. Depending upon the degree of failure, faulty EGR valve symptoms can range from mild to very pronounced.

Read more: What Are the Symptoms of a Bad EGR Valve? eHow.com- What Are the Symptoms of a Bad EGR Valve? | eHow.com



The EGR Valve consists of three major components:
l EGR Valve
l EGR Solenoid
l EGR Tube
The EGR Valve (3) is located at the right rear of the engine and is
attached to the right cylinder head, to the right of the Throttle
Body (4). The EGR Solenoid (2) is attached to the EGR Valve (3)
on the throttle body side of the valve. The EGR Tube (1) connects
the EGR Valve (3) to the rear of the Intake Manifold (5).


crankshaft position sensor maybe? No I don't think it would run period...

bad coil? No it would run like **** all the time if it even ran...