Frequent DPF regen related to boost leak

[John A]

Background:
Beginning of the week I got to work mid-regen. Rather than interrupt I let it finish while I waited in the car park.
Got in the van this morning to start an 60+ mile journey and the DPF was showing 25% full but within ten minutes it was up to 95% and began a regen.

Over the course of the 60+ miles on motorway and dual carriageway (with a bit of slow/stationary) traffic, a regen started at 65% (down to 29%) and then at 40%

There is a noise of an air leak - momentary under load, but my other half can hear it more constantly. My hearing is knackered and I no can’t hear the potential high frequency.

Differential pressure is somewhere around 9 hPa at idle.
I assume there’s a link between boost leaks and DPF regens?
I am yet to do any VCDS logging but is there anything I should look for?

 

[Stay Frosty]

I might easily be wrong but I don't think you can complete a re-gen just sitting with the engine ticking over at the regen minimum RPM, 1100 or thereabouts.
Most times this sort of thing happens you add a few more miles to the journey to get the revs higher and scorch the soot in the DPF.

 

[John A]

Apparently they will just do their thing and the concept of driving at a certain engine speed for a period of time is a myth.
I monitor the DPF with the app and see it will passively or actively regen under almost any circumstance, as long as the conditions for temperature at largely met. It’s not fussy on fuel quantity either, it seems, and will continue to regen in traffic.

Anyway I am getting an over boost code with VCDS which indicates there must be a leak.
Just need access to a smoke machine now.

 

[mmi]

Anyway I am getting an over boost code with VCDS

Share the code?

 

[John A]

5172 - Boost Pressure Regulation
P0234 00 Limit Exceeded (over boost condition)

 

[Bav]

I monitor the DPF with the app and see it will passively or actively regen under almost any circumstance, as long as the conditions for temperature at largely met. It’s not fussy on fuel quantity either, it seems, and will continue to regen in traffic.

I think that's the issue with trying to complete a regen in the car park - temperature is quickly lost when idling, often resulting in the regen being aborted.

 

[mmi]

Anyway I am getting an over boost code with VCDS which indicates there must be a leak.

5172 - Boost Pressure Regulation
P0234 00 Limit Exceeded (over boost condition)

Aren't those contradicting?

 

[John A]

I don't know, are they?

Searching those codes online and looking for the reasons why they come up has suggested a boost leak which could be in any of the induction pipework, or around the N75.
The accompanying whistle under load would suggest to me that there's some sort of leak, but I want to get some smoke through it first.

Whatever it is, it is affecting the way the DPF regens - so perhaps there is an EGR fault. It will show around 45%, trigger a regen and jump to 100% full.
I'm not getting any warning lights and the van is not going into limp mode, so I don't want to start throwing parts at it in the hope that one of them might fix it.

 

[John A]

I noticed the issue when driving to Stratford at the weekend and I’ve been under the bonnet with the torch and camera looking for an indication that there was an induction/pressure hose or vacuum leak.

Anyway, intercooler split.
So yes, boost leak, overboost fault, no fault codes, constant regen and boost leak whistle.

 

[hugh]

I noticed the issue when driving to Stratford at the weekend and I’ve been under the bonnet with the torch and camera looking for an indication that there was an induction/pressure hose or vacuum leak.

Anyway, intercooler split.
So yes, boost leak, overboost fault, no fault codes, constant regen and boost leak whistle.

View attachment 327133

Love that number plate !!!!

 

[John A]

My conclusions are:

The boost leak and subsequent repeat regens was not caused by completing a cycle while stationary.



A boost leak and/or a knackered intercooler will affect your DPF operation.