Technical Twin EGR issues - 'EGR Cooler Syndrome' Symptoms but different Fault Codes - HELP!

[deejays]

I had hoped to spend today sorting out a proper reply . but just seen @deejays reply and think he needs more data. The regen data is not as tight as he thinks. (one engine maybe)

Page 2 | DPF Regeneration

Passive regeneration is the third process in which the raised temperature attained durring normal running is high enough to burn off the excess soot in the DPF. The following examples (2 different engines) show this can occur in Ducatos but the...

www.fiatforum.com

This at least shows different engines.
mine can be from about 605C max to 670 max. I need to look at some historic data and check the temperatures and initial temp rate versus qty of fuel injected for regen. @Dancingbear It may be injector or injector demand (ecu) issue? There is no doubt its on the high side and the Ramprate 500-600 C @14C/s is much greater than my examples about 4C/s.

Just a quick response to your recent post where you say, “The regen data is not as tight as he thinks”.

I understand there can be a considerable range of DPF temperature variation during a regeneration and I have observed that with my known good engine. Below is another regeneration capture of my engine – it is not as tightly regulated as the previous I have posted and can be easily explained. But to explain that one needs to consider other factors that have a direct influence on the outcome. One must be careful not to become blinkered in the analysis by only comparing a few select parameters. The engine has many sensors, actuators and feedback loops and often demands a wider-angle lens to correctly view the analysis.

The temperature can be seen varying between 594C and 673C which is up there with some of the engines you have data for. The first graph has a vertical line drawn to indicate the maximum, and the second graph the minimum.

I have overlayed the vehicle speed, and it can be seen there is a direct relationship between the rate of vehicle acceleration and the DPF temperature during the regeneration – and this is to be expected due to the transient increase in exhaust temperature during acceleration – more fuel injected, more turbo boost etc resulting in higher and hotter exhaust gas flows.

 

[Dancingbear]

I think one needs to be very careful with AI assistants. For example, the references quoted from your ChatGPT post include this forum, as well as FB and other forums – so it is using references that may possibly be just opinion, hearsay or misquotes etc and could possibly lead to self-confirmation. So, next time it searches for answers, it may well come across your post of its response and self-consume to produce further corruption. Who knows?

It does however reference some quotes from the manufacturer FIAT, but even that has exposed some real issues. For example, it has stated “typical DPF temperature during regeneration ~700–800 °C; risk of thermal shock >1000 °C”. And then states that your maximums are well within the normal operating band! Further, it concludes with “Conclusion on Regen 2: By numbers, Regen 2 looks technically normal: correct temperature band, …” What absolute BS!

I know exactly which copyrighted FIAT document that was scooped from as I have read it. But those figures were taken from a general preamble discussion about the DPF materials and material specifications during a comparison discussion of the then current FAP system used by other manufacturers. Within that same very old document and several later references can be found that the DPF temperature must reach a minimum of 580C for an active regeneration, with typical operating range of 600C – 650C. And those figures are confirmed by our practical measurements of good engines.

Another issue is that it has stated it could not find any official FIAT documentation that referenced the injector correction tolerances and could only state it found some unsubstantiated information from MES, 2 FB + 2 other unnamed references. Well, it couldn’t have looked too bloody hard is all I can say! (I hope you were using the free version and not paying for such advice). Perhaps next time, after reading and scooping this it might reference FCA Service News 10-023.19 of 20/11/2019 and a much earlier FCA Service News 10-17.09 of 14/04/2019. I prefer to use my own intelligence.

But, after all that, it has basically agreed with my diagnosis – I suspect that the DPF is damaged and causing the issue which is why I suggested the first thing you do is take a borescope and investigate the downstream side of the DPF and also check the Post DPF temp sensor.

It has even suggested a parameter list for testing – which you have already done (my suggested template) to rule out any other possibilities. Be aware that DPF damage may not be obvious downstream as the filter medium may be damaged internally, or even on the upstream surface area. The upstream Catalytic Converter may also be damaged.

The other issue you need to keep an eye on is the new throttle body for correct operation as previously stated as it was completely open for the entire recent test run.

Just to confirm something. I have recently read a trusted document that validates my earlier reverse engineering musings, and that is the DPF Temp sensor is the “Policeman” and is the sensor responsible for triggering MAX TEMP cut-off to terminate the regen if the maximum allowable temperature is exceeded; and the Post DPF Temp sensor is used for the desired regulated regen temperature (in coordination with the DPF temp sensor). This adds to the weight of what is causing the regen termination – as previously shown by the diagnosis there is something malfunctioning to cause the Post DPF temp sensor from reporting the correct Post DPF temperature fast enough – it is either under-reading (sensor malfunction) or the bulk of the exhaust gas flow is bypassing it due to some form of internal damage to the DPF. I suspect the sensor is probably OK, as it eventually reports near correctly after some time lag, and it also follows closely the other temp sensors as expected prior to the regen occurring. It is the rate of the Post DPF temperature sensing that is the issue, and that can be explained by exhaust gas bypassing the sensor due to internal damage to the DPF.

Yes I agreee with everything you say. I also found that document later last night and the high 'normal' temperatures it quoted appeared to be for a euro 5, presumably single egr variant

I tried to separate the exhaust / DPF flange last night to boroscope.. the nuts are completely f****d... I'll check out the x 2 temp / o2 sensor ports tomorrow hopefully I can boroscope the post DPF temp sensor and the check sensor soot accretion / physical integrity at the same time!? I will also capture somre more data for the throttle body!

Thanks again, every day a school day!!

 

[theoneandonly]

@deejays i wasn't trying to be derogetory just giving a wider view of normal. Have you a copy of your latest CSV file? As previouly said DB results are different ie a more rapid rate of change (due to greater fuel injection) seen in your graph and the table for first 5 injection value (@MM3/i also affected by rpm).

 

[deejays]

Yes I agreee with everything you say. I also found that document later last night and the high 'normal' temperatures it quoted appeared to be for a euro 5, presumably single egr variant

I tried to separate the exhaust / DPF flange last night to boroscope.. the nuts are completely f****d... I'll check out the x 2 temp / o2 sensor ports tomorrow hopefully I can boroscope the post DPF temp sensor and the check sensor soot accretion / physical integrity at the same time!?

Thanks again, every day a school day!!

Those suggested chatGPT temps don't even apply to the E5 engine.

 

[deejays]

@deejays i wasn't trying to be derogatory just giving a wider view of normal. Have you a copy of your latest CSV file? As previouly said DB results are different ie a more rapid rate of change (due to greater fuel injection) seen in your graph and the table for first 5 injection value (@MM3/i also affected by rpm).

I agree, I don't think you were being derogatory either - no offense taken or meant. I could post that csv file - no issue with that, in fact I was thinking of posting it, but the reason I haven't is because of the parameters set I was using at the time. It was not set for a DPF Regen and is missing a number of parameters to make sense of it. It was just by chance that a regen occurred and it is missing the other two temp sensors, the gas pedal % (really important) and throttle opening. I would rather post a file which has the correct parameter list - so next time a regen is due I will record it.
What is really different (and really important) in DB's files is the mismatch between the rates of temperature increase of the Post DPF sensor relative to the DPF sensor. This is the critical difference. Even if the fuelling is different for some other issue, the relative temp increase should still follow, but it does not - it is extremely different. The increased fuelling is most likely a direct product of that because the post injection rate is driven by the Post DPF temp sensor - and it is screwed, thus the injection is screwed.

 

[Dancingbear]

Just a quick response to your recent post where you say, “The regen data is not as tight as he thinks”.

I understand there can be a considerable range of DPF temperature variation during a regeneration and I have observed that with my known good engine. Below is another regeneration capture of my engine – it is not as tightly regulated as the previous I have posted and can be easily explained. But to explain that one needs to consider other factors that have a direct influence on the outcome. One must be careful not to become blinkered in the analysis by only comparing a few select parameters. The engine has many sensors, actuators and feedback loops and often demands a wider-angle lens to correctly view the analysis.

The temperature can be seen varying between 594C and 673C which is up there with some of the engines you have data for. The first graph has a vertical line drawn to indicate the maximum, and the second graph the minimum.

I have overlayed the vehicle speed, and it can be seen there is a direct relationship between the rate of vehicle acceleration and the DPF temperature during the regeneration – and this is to be expected due to the transient increase in exhaust temperature during acceleration – more fuel injected, more turbo boost etc resulting in higher and hotter exhaust gas flows.

View attachment 476330

View attachment 476331

I am really interested to see how the next regen looks by comparison - i am staying mindful that the assumptions around unregulated temperature in my vehicle have only really been witnessed on 1 regen cycle (and a bit for the failed one)... and according to the data, that regen occurred at speeds ranging from 18 - 72 kph - and as you state this alone could cause significant fluctuation. i can see there is a wide range of speeds in your graphs above too but they are higher speeds - perhaps if my next one is done at motorway cruise (and it doesn't fail!) it will present with a more controlled / stable temperature profile???

 

[Dancingbear]

However, in the two latest files it is being shown as fully open, only traversing from 0.05% to 0.36% - so something is amiss there

Hi again @deejays @theoneandonly , i've done another road test specifically to assess the throttle body. @deejays You rightly identified that my new throttle body was running a few % lower than my old one, and to what you would expect based on your own observations (and assuming my old one was functioning normally to the point of failure (?))

Having taken a deeper look, the line quoted above where you suggest opening of 0.05% to 0.36% in one of my .csv files seems actually to be throttle position, as opposed to throttle valve opening - a different parameter. The graph below indicates 'throttle valve opening' comparisons for 1) the old throttle body, 2) the new one once fitted and 3) the new one today.

The variations you initially identified are still visible but thankfully nothing as wild as 9% down to 0.05%... I have to assume the old one was functioning normally (until failure) as the parameters matched your expectations. The new one, although 2-3% less closed / more open appears to be reasonably stable and consistent - could this be down to environmental conditions etc??. Hopefully as the graph suggests it is functioning consistently and query 'normally'!? - unless you've a further insight this has gone onto the 'monitor / no further action required' list for me!?

 

[deejays]

Hi again @deejays @theoneandonly , i've done another road test specifically to assess the throttle body. @deejays You rightly identified that my new throttle body was running a few % lower than my old one, and to what you would expect based on your own observations (and assuming my old one was functioning normally to the point of failure (?))

Having taken a deeper look, the line quoted above where you suggest opening of 0.05% to 0.36% in one of my .csv files seems actually to be throttle position, as opposed to throttle valve opening - a different parameter. The graph below indicates 'throttle valve opening' comparisons for 1) the old throttle body, 2) the new one once fitted and 3) the new one today.

The variations you initially identified are still visible but thankfully nothing as wild as 9% down to 0.05%... I have to assume the old one was functioning normally (until failure) as the parameters matched your expectations. The new one, although 2-3% less closed / more open appears to be reasonably stable and consistent - could this be down to environmental conditions etc??. Hopefully as the graph suggests it is functioning consistently and query 'normally'!? - unless you've a further insight this has gone onto the 'monitor / no further action required' list for me!?

View attachment 476355

Oh bugger! You are correct - I have in error put the wrong parameter in the REGEN Parameter Template 0! The correct parameter is Throttle Valve Opening, and not Throttle Position. Thank you for picking that up - just shows we can never be too careful. I will see if I can correct that in the Guides section - but I don't think I can. In the meantime, I will add a correction in the discussion tab for it. Please update your Template 0 for this correction.

 

[deejays]

I am really interested to see how the next regen looks by comparison - i am staying mindful that the assumptions around unregulated temperature in my vehicle have only really been witnessed on 1 regen cycle (and a bit for the failed one)... and according to the data, that regen occurred at speeds ranging from 18 - 72 kph - and as you state this alone could cause significant fluctuation. i can see there is a wide range of speeds in your graphs above too but they are higher speeds - perhaps if my next one is done at motorway cruise (and it doesn't fail!) it will present with a more controlled / stable temperature profile???

Perhaps, maybe... We shall see... If what I suspect is occurring is correct, then the higher the Post DPF Temp is just prior to the initialisation of Post Injection occurring , then that may help, and to achieve that the vehicle needs to be at higher speeds/loading before Post Injection starts. But, not soon after it starts, to try and prevent a large overshoot, then it may perhaps be better to then reduce the engine loading and thus speed back to around 70 - 80Kph.
And thanks once again for being sharp and picking up the incorrect throttle parameter. The new throttle body would appear to working fine - even though there is a slight % difference - I don't think that is of issue - in fact it may be because of the possible lower temp being reported from the Post DPF sensor.

 

[Dancingbear]

So, i removed the post DPF temperature sensor and boroscoped the downstream end of the DPF. Movie attached

Findings:

1) the temperature sensor was soot free, straight, looked undamaged, came out and back in trouble free.
2) the inside of the dpf is, frankly, the cleanest place on the whole van!!!??? This confuses me - there are no signs of breakdown, broken seal around the edges, loose parts, soot or anything else suggestive of a problem. The fine particle filter looks intact, there is no soot evident on the filter anywhere. The exhaust tube and the feed to the LPEGR were visualised and appeared soot free and undamaged.

To be honest i was expecting to find a horrible mess in there which matches the soot in the exhaust, but there is none!?

I am no expert and happy to be proven wrong, but given the soot in the tail pipe I was expecting to see at least some damage in this part of the DPF???

Possible summaries:

1) the dpf is fractured but i didn't see the damage. Perhaps the gas comes out hot / pressured enough to go straight through without leaving soot and then condenses / cools etc down stream where the soot collects???
2) I've looked at the wrong part - the 'sparkly' matting in the movie is the terminal end of the DPF 'can' and not the fine end of the filter???
3) the DPF is in good condition but a dirty replacement tail pipe / exhaust box was fitted before my ownership which continues to corrupt the tail pipe?
4) soot is coming against the flow through the LPEGR cooler - but this does not make sense and would surely be a significant failure throwing up fault codes etc?
5) there appears no other way for soot to get into the tail pipe so why is the DPF and the outlet so clean?

Of course this doesn't address the freaky temperature profile of the regens or the failed regens, but as i said earlier I have only captured 2 regens and will continue to capture as many as possible. Could ash (as opposed to soot) be blocking the dpf creating a solid mass which skews the heating profile for regen (but differential pressures don't support this?)

I honestly don't know what to make of this now.

The plot thickens

Thoughts?

 

[deejays]

Hi DB, I have a cheap borescope and I have to admit it does not give me the clearest of pictures either, and it can be difficult to clearly see details. (I should have paid a bit more money – probably a lot more, but I could not justify it).

Yes it does look generally really clean, except for just one of the filter core bricks. I suspect you may have found the issue as that one brick is markedly different to all the others, and it even appears it has been compromised on more than one edge where it is bonded to the adjacent brick. It also appears to be compromised on part of its general surface area as well.

Have another real close look at your video. It is easier to see in the video, but below are a number of captured screen shots with time references attached.

It is likely that this is the source of the soot and the exhaust gas bypass of the Post DPF temperature sensor. Like you, I am no expert and am not claiming to be.

5 Seconds:

8 Seconds:

10 Seconds:

32 Seconds:

40 Seconds:

49 Seconds:

54 Seconds:

 

[deejays]

Hi DB, I have just had another look at your video and I can see there is another filter core brick that has suffered damage. You can observe it (fleetingly) at around the 18 second mark. It is the second one to the left of the first one I spotted (as viewed in the video). If you (or anyone else) are having trouble finding/seeing it it could be due to the colour accuracy of the monitor panel you are viewing it on. My monitor is certified wide gamut, HDR certified and calibrated. Some monitors will have trouble showing fine gradation when it comes to grey. If it is not clearly visible then adjusting the embedded video settings may help. I suggest turning down the brightness, turning up the contrast and even the saturation if needed. Below is an example of the first one I spotted:

And the following is the second one around the 18 second mark (possibly also showing a third one behind it):

 

[Dancingbear]

@deejays im led to believe this boroscope is worth significantly more than the van!! And the screen picture was really good, but the challenge is obviously knowing what your looking for - I was expecting it to look like the bottom of a coal bucket in there

I was recording quickly, filming the boroscope screen with my phone (don't ask why!!) but as you've now pointed out the darker areas it does make sense, although still doesn't explain why it's generally so clean? The tail pipe is filthy, so I can't understand why such a difference.

There is company here in the uk who recondition OEM DPFs - I'll ask them if they'll take a look at the footage and go from there!

I'll keep you updated, thank you

 

[deejays]

It is clean where there is no damage, but not where the soot is coming through.