I have a 2010 XF S/C CPO. When I drive the car for any semi-long distance 45mins to 4hrs, it varies that the problem may arise. What happens is I will have been driving on the turnpike for 1hr at a constant speed, after I have stopped to go through the gates when I try to accelerate the car surges. It will not accelerate constantly, it goes vroom vroom vroom vroom, until I get so pissed I floor through it. Putting it in sport and or dynamic mode does not cure the problem. Sometimes the check engine light comes on and sometimes it doesn't. The light will then stay on for maybe a few hours, even through times of me turning the car on and off. I have had it to the dealer once before and they told me there was a new engine flash that should cure the problem, it didn't. The dealer just picked it up again this morning and of course the light is not on anymore. Any help would be greatly appreciated.

 

They should still be able to pull the codes, as once the CEL comes on the codes get stored in the computer.

 

That's what they said last time. I imagine they got the code last time and thought they fixed the problem with the software flash.

 

Doesn't sound like it may be anything significant, but keep us posted regardless.

 

They said they found mass airflow faults and replaced both air filters. We'll see what happens.

 

Ah, there have been reports of air leakage underneath the intercoolers on 4.2 cars. This is time consuming to fix.

This sounds very much like incorrect diagnosis. Lean mix fault code misinterpreted as airflow through the filters. Unlikely to be the fault. They should be looking for an air leak downstream of the AMM.