C4 2008 - Engine hesitates or pulsates at low rpm/idle

[jokre]

Car:
Citroen C4 2008 1.6 HDi 110 9HZ/80kW

Problem:
When idling after a cold start, it runs OK (i.e. steady rpm), but when coming home (or parking somewhere after driving) the idle is pulsating (about 800 rpm, then up to about 1000 rpm, then back to lower rpm, and so on up and down). Also, when driving the car it hesitates at some points. For example, when driving at 40 km/h with no foot on the gas pedal and then pushing down the pedal to maintain speed, the engine hesitates for a short while like it's choking and short after that it gets up to speed again and runs as normal. Apart from the annoying pulsating and hesitating behavior, most of the time the engine runs totally as expected. Turbo spins up and the rpm is steady, i.e. it doesn't constantly hesitate or "pulsate" when driving it on the road.

Changed (brand new):
- MAF sensor
- EGR valve
- Camshaft cover
- Pipe from MAF to turbo
- "Pipe" from turbo to first hose (in front of the camshaft cover)
- All IC hoses from the turbo to the intake
- Intake pressure sensor
- Intake temperature sensor
- Air filter

I'm kind of out of ideas at the moment and it feels as if I have changed most things that could be the source of the issues. Apparently, there are other sources of issues since the bad behavior still remains after renewing/changing the things mentioned. I've managed to find some posts/threads but the ones I could find points to parts that I've already changed on the vehicle.

[mickthemaverick]

To complete your replacement programme I'd fit a new fuel filter and see how it goes.

[PaulC5]

After replacing the fuel filter you need a diagnostic if not already done. Replacing parts without one hoping to find a faulty part can prove to be expensive.

You could also check the doser valve, on our 2008 C4 it leaked oil but did not cause any problems but if left the oil going onto the alternator might have given problems.

[jokre]

Thanks for the suggestions. I will replace the fuel filter as the next step and see if that helps. Running diagnostics doesn't show any fault codes that should be relevant to how the engine performs (or not performing).

[jokre]

Changed the fuel filter now, didn't change anything really. (No oil on the alternator either, btw).

[Estately]

Must admit, expected the fuel filter change to cure the problem.
Can you identify if air is getting into the fuel line?
Fuel often doesn't appear to leak out but air can get in, probably only needs a small amount of air to give the symptoms you describe.

Hope that helps.
Andy.

[jokre]

Could injector seals be an issue here?