I have a pain in the butt recent problem, intermittent hunting or lumpy Idle.
Original fault was poor starting, so :
New injector seals ( discovered injector roller mis-aligned and scoring cam so fitted new cam and injector rockers)
New Glow plugs
New MAF MAP and ATS
EGR deleted 2 years ago
Now starts perfectly (half a turn), but appears to have developed this annoying & intermittent fault.
So I cured the starting problem, but trying seems I now have another problem!
To diagnose this fault I found a serious imbalance on two injectors, so replaced them as well.
The clutch spigot bearing does make a noise for around 60 seconds when first driving, but it has always done this.
Crank Position sensor?
DMF on the way out?
Clutch switch?