C5 HDI 16v hesitation/hunting

[red_dwarfers]

This last week I've noticed my C5 2.0 HDI 16v 6spd manual is hesitating/hunting probably around 60% of the time.

It's only very minor, probably around 50-75 rpm variation.

I notice it intermittently under these circumstances:
Idle when starting the car from cold and hot
Motorway using cruise control
Driving at a steady speed using pedal
Steady acceleration

I have never noticed it:
When engine braking

It will generally pass after a few minutes and come back again a bit later.
If I change gear while it's hunting, it feels like I'm "catching the engine out", the gear change then isn't very smooth. I work around this by giving it a few more revs than I usually would.

The car has an easy life, of the 2000 miles a month, probably 80% is on motorways and rural A roads.

I've ran diagnostics using a Lexia and there are no related faults reported.
In January it had clutch, DMF, belts, tensioners, gearbox oil, engine oil and filter, air filter.
I gave it an Italian tune up on Friday.
Yesterday it had another engine oil and filter change and fuel filter.

[GiveMeABreak]

I had the very same problems on my DW10BTED4 engine on the MK II Facelift C5 I had. Cruise kept disengaging, hunting and hesitation on idle - and this started off very intermittently over the months and I replaced the MAF to no avail. Over the coming months it got worse and worse until it started making rasping noises, with lack of power. I managed to keep revving and gently engaging clutch just to get some power to get home from work one day.

Got it towed to the garage as I wasn't going to drive it like that - and they finally found the cause was a split in one of the air hoses - it was a very small one and very hard to detect it (I can't remember back which one it was now unfortunately), but they replaced that and problem solved. They were thinking about DPF problems - but there was nothing wrong with that - so persevered and found the leak.

[EDC5]

So would the air hoses concerned be part of the vacuum actuation system for the EGR, VNT Turbo and air Doser?

I suppose any one of those systems not actuating correctly could restrict airflow and cause rough running.

[GiveMeABreak]

I suspect it would have to of been - but annoying that I can't remember now as I was contemplating DPF replacement and was just relieved that it was a hose!

[red_dwarfers]

Thanks very much!
I'll have a nose at the pipes.

[wurlycorner]

Is the turbo any more noisy (whistling)?
This would be indicative of a leak on the high pressure side of the intake systems and could cause the symptoms you're talking about. Mine currently has that, I just haven't managed to locate the leak yet