1.6 HDi Idle hunting

[tPt76]

Hi,

I came here in a desparate need of assistance. My car is in fact 2008 Mini Cooper D, but it has got a 1.6 PSA diesel engine, with 109hp, I believe which is used in multiple Citroens and Peugeots as well, so I would think that there is much more of experience of those engines in this forum than in Mini forums.
The problem is hunting idle. The idle drops gradually and then suddenly recovers. It occurs at regular about 5 sec. intervals.
If I unplug either MAF or EGR, the idle is steady.
MAF, MAP, EGR, Injectors and turbo have been changed, but none of these have had an effect with the issue. Haven't found any leaks in the hoses. Any help would be appreciated.

[shtu]

Examine the correction values across injectors or the injected value for each, you may find one or more are out of line, which hints at faulty injector(s). Not uncommon with the Siemens\Continental\VDO injectors.

Have a look at my assorted threads on this topic, lots to read there.

[tPt76]

Injectors have been replaced, with no change in symptoms

[Muir]

What are your intake and outside temp sensors reporting, do these values seem plausible?
Intake air temp will of course be some degrees higher than your outside temp reading, but probably only by 5-7 degrees.
Both sensors can affect engine behavior.

Also it might be worth looking at the EGR control solenoid if it's vacuum operated.

[shtu]

Injectors have been replaced, with no change in symptoms

Yes, but what are the correction values?

Changing the MAF, MAP, EGR, Injectors and turbo suggests that there's been no diagnosis done, just multiple firings of the parts cannon.

What evidence was used to justify spending, what, 2000 euro on parts and fitting?