XK Engine Stalls: EVAP System Malfunction Warning

My 2010 XF had a similar issue last winter. Based on some experience working on cars, the symptoms you describe match what I encountered, check engine light and stalling issues pointing to an EVAP system failure. The root cause in my case was a defective activated charcoal filter. The workshop ran a smoke test which confirmed a leak in the EVAP system. The pressure sensor was giving incorrect readings because the charcoal filter was no longer properly filtering fuel vapors. The total repair cost was 275€ including diagnostics, parts and labor. Since getting it fixed, the system has been working perfectly with no more stalling or check engine warnings. To help provide more specific guidance: What error codes is your check engine light showing? Have you noticed any fuel smell? Does the problem get worse after refueling? Has the fuel economy changed? These details would help determine if your issue matches the leak detection problems I experienced. While the XK and XF share similar EVAP system components, knowing these specifics would confirm if we are dealing with the same root cause.

Thanks for sharing your experience. I had my last service at 111000km about 2 months ago, and after reading your reply, I checked the error codes. Getting P0455 and P0442, both related to the EVAP system. The fuel efficiency has dropped noticeably, around 15% worse than usual. No fuel smell detected, but the stalling seems to get much worse right after filling up the tank. The air flow sensor readings look normal though, so that rules out some potential causes. I will get the smoke test done as you suggested to pinpoint if the charcoal filter is the culprit in my case too. A system failure like this is quite concerning, especially since the purge valve was replaced during the last service. Will update once I get more diagnostic results.

Thanks for the follow-up details. Those error codes definitely align with my experience, both P0455 and P0442 showed up on my XF as well. The increased stalling after refueling strongly suggests a faulty charcoal filter, exactly like my case. The recent purge valve replacement adds an interesting twist. My mechanic explained that a new purge valve working with a degraded charcoal filter can actually make symptoms worse, as it tries to compensate for the system failure. This would explain your 15% drop in fuel efficiency. When I had my repair done, they found that the charcoal filter had completely deteriorated internally, causing the pressure sensor to read incorrectly. The smoke test should quickly reveal if you have the same issue. The fact that your air flow readings are normal is also consistent with my experience, the EVAP system problems dont always affect those sensors directly. Quick tip: while waiting for the diagnostic results, try not to fill the tank completely full. This helped reduce the stalling frequency temporarily in my case by limiting the vapor buildup.

Really appreciate the detailed explanation about the purge valve interaction, that actually makes sense why things got worse after the service. I will follow your advice about not filling the tank completely for now. I contacted the workshop and scheduled the smoke test for next week. The quoted diagnostic fee is 90€, which seems reasonable given the emission control system complexity. The service advisor mentioned they stock the charcoal filter parts, so if that turns out to be the problem, they can do the full repair same day. The system failure symptoms match your case so closely that I am hopeful this will resolve both the fuel efficiency drop and the stalling issues. Will definitely post an update after the smoke test reveals what is actually causing the pressure sensor to act up. One last question, after your repair, how long did it take for the check engine light to clear and the stalling to completely stop? Just want to know what to expect if I end up needing the same fix.