Citroen c4 2.0 hdi turbo surging

[August]

The car in question - Citroen c4 2013 2.0 hdi 110kw 6 speed manual.
When accelerating under load, exhibits a 'pulling back and forth' sensation (momentary power loss/surge) specifically around the 1800 RPM range, accompanied by a 'chut-chut' or surging noise from the turbocharger during acceleration. Then it throws "Engine faulty" on the radio screen and momentarily flashes "service" light on the dash, but no check engine. After that car seems to be in some sort of a limp mode. Restarting the car resets it.

When accelerating softly past 2500rpm or so, and then pressing full throttle its seems to do just fine no surging.

I've noted oil residue near air doser/shut of valve control rod. My question how does the shut of valve work, does it work like on/off switch or does it open close gradually following engine load? What is the natural resting place of that valve and can i by pass it somehow in order to diagnose?

thank you

[mickthemaverick]

You need to have a diagnostic session with a high level kit, preferably Diagbox, and see what fault codes are stored. It sounds like a fault in the turbo area but it could be a fair number of issues. The diagnosis should help narrow it down.

[August]

So it doesn't seem to be some sort of a common problem for these engines?

[mickthemaverick]

I don't recall hearing of it before!