Hello,
My JAG (XF 2.7D), when on higher gears (4th sometimes 5/6 usually) and accelerating lightly, has RPM fluctuations.
It gets down slightly then gets back to the previous position. It happens until I shift the gear to the lower one, or accelerate harder. It seems like the engine is suffocating a little bit at that moment. There is also a sound (seems to come from underneath) for that moment when the RPM is at a drop point.
I have changed MAF (there are 2), the computer diagnostic readings are alright for the airflow.

Sorry if I have missed the same topic somewhere in the forum, but I was unable to find one so I created a new thread.

 

At the drop moment, the sound from underneath seems like a vibration. All the fluctuation seems to be periodic.

 

I also have a 2008 XF 2.7D with the same characteristics, although mainly in 5th gear. RPM fluctuations and strange sound exactly as you describe.
My XF has over 190,000 miles on the clock and I have had if for 18 months. I was a bit concerned when I first noticed, but it hasn't caused any problems or got any worse. I recently drove from the UK to Croatia for a holiday, a round trip of 3,000 miles without incident. I'd like to know what is happening, just for peace of mind, so please add an update if you find anything.

 

It hasn't caused any problems for me either. However, I thought it might in the future. I hope it is nothing serious, but still want to find the cause of it. Will let you know if something comes up.
I still hope someone from this forum will explain more about this issue.

 

Does anyone else experience this? Any advice?

 

I had a similar thing ( and a few others) with a petrol version after a tune. slight surge when at constant speed when more torque was requested (incline in the road, bridge etc) . Lie 100 rpm. Very annoying. especially with cruise control set. Was not so pronuonced at very high speeds (over 75 MPH It was fixed with a new tune.

Have there been any software updates for the 2.7D perhaps?

 

Could you please elaborate on "tune". is it the ECU tuning known as "chipping"?
How can I check if there are any software updates for 2.7D? We do not have JAG official dealer in my country.

 

Sorry yes, ECU tune.

If you are stock you should see if the current software version is updated

 

Where can I see if it is updated?

 

Since you don' thavce a dealer nearby you shoudl think about getting a SSD device to repair your car

 

Old Thread, I know, but have any of you ever figured out what the issue was / got it fixed?
I have the exact same issue on mine (XJ 2.7D). The noise when the RPMs drop sounds like turbo compressor surge.