This is exactly the fault I've got on my '406 (same engine!!!) as well!!! If you accelerate to about 4000 rpm you can feel a bit of a surge but it's not very much, and you can barely get over 60 on long uphill motorway inclines, and on steeper hills on all-purpose roads, such as round Leek and Ashbourne for instance, it struggles to get to over 35!!!Bought a C5 2.0HDi only a couple of months ago. Has driven superb up until now but now am noticing a serious loss of power. When accelerating my foot seems to be right to the floor. I have no overtaking power at all. I've no warning lights, no 'limp home' warnings, no 'service warnings'. Car just seems to have no guts. The engine doesn't appear to want to go anywhere over 3500 revs, It just sounds like it's screaming.
I can't get my PP2000 software to activate on my lappy yet so haven't read anything out as of yet!!!
Suggestions please?
Chris Williams
PS!!! Engine and oil temps both exactly "90" once warmed up (engine coolant temp a bit lower on cold days) and I can't hear any untoward noises from anwhere or any whistles like the author of the quoted post - just no ooooomph at all!!!