1.6 HDi cutting out on idle and "yank" while accelerating slowly

I have a strange problem. It's a C3 HDi -07 with the 109hp engine. Has DPF. I've had it for about 6 months and have been driving about 12000 km so far. Has 180000km on the meter (sorry if my english isn't perfect).

Sometimes (quite often) when I start it (cold) it's cutting out efter 4-5 seconds. Not always but the idle is "dipping" and will do so every 4-5:th second regularely and sometimes the dip is so deep that the engine stops. Usually on the first dip. It can also happen when it's warm but that is very rare.

The EGR-valve was suspected so it has been replaced with a new one. No change.
Glow plugs have recently been changed (two were bad). Both air and diesel filter were changed last year.
Diagbox/Lexia shows nothing, no error codes or other clues. Engine lamp is not lit.
No leaks can be heard or has been found.

Another thing is that when I accelerate slowly I can easily feel (in the pedal) that it yanks (very little) and this happens regardless if it's warm or cold. If I give it more gas it will stabilise. It's about the same phenomenon on a petrol engine if a vaccum hose is bad or the intake has a leak.

I also think that the fuel consumption is a little bit higher than it should be (5 liter/100 km on higway, should be closer to 4).
It always starts easily and I have no other issues while driving. It's quick and fun to drive but these problems - that has been escalting - is bugging me.

My question to you HDi experts is: what is your best shot?
One or more injectors? MAF? Any valve? And how can I use Diagbox while the engine is running to pinpoint the problem?

nizzehult wrote: ↑Thu Sep 27, 2018 8:22 pm
My question to you HDi experts is: what is your best shot?
One or more injectors? MAF? Any valve? And how can I use Diagbox while the engine is running to pinpoint the problem?

Hi nizzehult.

Your problem is that there are no error codes stored. This would indicate a problem with a power feed (12v/earth) to an ECU that stores the codes (BSI) or an unmonitored fault, like the low pressure fuel pump in the fuel tank found on some models.

With no error codes, I don't think lexia will give you any extra information.

Injectors and MAF are both monitored by the BSI and available as fault codes in lexia, so it won't be those.

Hi!
I understand you fully; if I had a stated error code it would be much easier to pinpoint the problem. But remember that good mechanicans fixed complicated errors even before there was computers in cars...
I work with computers/servers. On computers, error codes can clear out themselves if the error disappears within seconds/minutes (if it's a minor error or just a "glitch"). I don't know if it's the same with cars.
Another theory is that this fault is within the tolerances and if you know where to look in Lexia there is a chance that the glitch can be found. I think there is a way to save measuerd data for analysis, right?
I think that if it would have been related to the low pressure fuel pump it would show when accelerating fast.