2.0 BlueHDi EAT6 engine tone and vibration change at idle

[dec_90]

Hello everyone,

I'm looking for some advise if possible about a strange problem that has surfaced recently.

Firstly, my car is a Citroen C4 Grand Picasso 2017, 2.0 BlueHDi 150, EAT6
Recently I had the DPF and EGR disabled.

The problem : Weird engine tone and vibrations after 40s of idling

Basically the car idles great, but if I stay at a red light for 40-ish seconds the engine tone changes (becomes more labored) and there is a noticeable increase in vibration (could be classified as a tremor) . RPMs during this do not change still stay at around 750.
If I increase the rpms to or more than 1000 and again return to idle rpm the car goes back again to idling smooth (no labored engine tone or increased vibrations) but again after the same time (40-ish seconds) the abovementioned problem appears. Generally if I get lucky with the red lights and don't stay idling for long I forget about the issue.
I wonder what could be causing this effect. Could it be a bad EGR delete tune or bad DPF delete tune. How can one spot a bad tune ? What does the car ECU check at that 40-ish second marker and what does it change in order to cause this engine tone and tremor (like air/fuel/injector timing)?

P.S

I have changed the big engine mount on the right side of the car recently and made the car feel like new. Because of that I do not think that the engine mounts are an issue here (also that the problem appears and disappears in a controlled manner).
Excluding this problem the car runs great.

Regards

Dan

[mickthemaverick]

I am afraid the forum does not condone any interference with the emission control systems and hence we are unable to comment.

[dec_90]

Hello all again,
I have reinstalled the DPF and EGR.
The above mentioned problem has disappeared.
But I have noticed something else perhaps not related to the EGR and DPF at all.
Basically I still do not like the idle of the car, meaning RPM are fine and steady (750) but sounds a tad louder (maybe more drone-nier) and tad more vibrations than when I got the car a year and half ago. Interesting thing is that, if I put the A/C on, the idle smooths idle perfectly. So I was thinking perhaps of raising the idle rpms from 750 to 800-815 but preferably would like to find the culprit for 750 harsh idle.
Any suggestions are appreciated.
Again to mention the top main engine mount is new, perhaps I need to change the rear one (PSA 9804890680)

P.S.

Since turning the AC on fixes it, could it be possible that the auxiliary belt tensioners to be going bad and causing this AC off bad idle feeling ?

[Ceenine]

Mine does it too. Patiently awaiting an answer from a knowledgable soul.

[Huskyxantia]

If it ain't broke don't fix it. The system was fitted for a reason and can land you with a hefty fine if its removed , admitting on a public forum as well is just plain stupid. Sorry but no ones above all the crap laws .

[Huskyxantia]

As for pulley belt tensioners they would make a noise but I don't thing they would cause and change engine performance.