407 2.0 HDI Engine Surge

[Echuca 407]

My 2005 407 2.0 HDI has started suffering engine surge under light, trailing, or steady accelerator. Not evident under acceleration or deceleration in normal road use but is very evident in "around a country town" situations where the traffic light grand-prix doesn't exist. I'd be grateful for any ideas.

 

[UNM]

I had a similar problem with my 2008 407 HDi. An EGR blanking plate fixed it for me.
You can make one, or buy from eBay/Aliexpress. Worth trying as it is quick and easy to install.
I installed one with a 10mm hole so it doesnt completely block the EGR, just removed the surging.

 

[gromzx]

I had the same problem with my 306 HDi. It also was worse when the engine was cold, especially on a cold morning.
It was the fuel suction valve on the HP pump in my case.