DPF Frequent regens CUPA engine code

[Billycool]

Hi Guys,

Like a lot of people I'm getting frequent DPF regens. 120+ miles down to about 30.

SEAT Leon ST FR 184 CUPA engine code. 155,000 miles.

Regens were becoming more frequent, ash level was increasing.

July - had an o2/Lambda pre-cat error. Fuel consumption suffered so replaced that and fuel consumption increased. DPF regens dropped from 50 miles to about 35.

November - decided to get DPF chemical cleaned on the car. Seemed to go okay. Ash level reset. Unknown to us, the DPF pressure sensor got damaged and melted the next time I drove it. When you Google it, it turns out it happens a lot, usually after a timing belt change. Replaced DPF sensor and got it adapted. Idle hpa was 20 and was told that's about right.

Drove the car and it still regens every 30 miles are so. I thought that I should replace the post-cat o2 sensor in case that is causing an imbalance with the newer clean sensor. After much searching online and being under the car 3 times, it turns out the CUPA does not have a post-cat o2 sensor. Who knew!

It seems that like other posters, the measured soot level is increasing at a much higher level than the calculated. The measured then triggers a regen. Previous soot levels were around 100 mg/m cold and 40 mg/m when warm. That would cause a regen every 120 to 180 miles depending on journey type.

Currently, the soot levels have jumped up to over 12,000 mg/m. That is mentally high. Only last week, the car was on 92 mg/m and jumped up to 12,811 mg/m a mile later and started a regen after 28 miles.

So - what is influencing that calculation? If I know that, I can hopefully find the source and fix it.

Some info:

• New pre-cat o2 sensor added - not adapted but is supposed to learn over 1000 miles anyway, so hopefully not an issue.
  DPF cleaned and ash level reset. Was doing freq regens beforehand but not got any better.
  DPF sensor replaced and adapted. Idle hpa of 20.
  New DPF plug fitted - this was spliced in with a block connecter - I'm checking the voltages tomorrow to make sure this is not causing a data error (no fault code shown)
  DPF pressure pipe seems clear (have blown some air through it - not very scientific though)
  Car uses a little oil but the EA288 does anyway
  Oil and filter changed every 5,000 miles with 507.00 oil
  Car runs fine

I think the frequent regens are linked to the measured soot level - I'm just not sure what is making it think that.

I'm open to to ideas before I risk replacing stuff unecessarily.

Thanks.

[admin]

Thanks for the hyper detailed post, it isn't common on the web and I'm sure it can help many other users.

About your question on the soot charging rate, it's calculated by the app and it isn't coming from the ecu. Its very high number depends on the soot mass calculated value that can jump from a low value to the field soot limit (near 24% of charge) when the ECU forces the regeneration. When the ECU wants to regenerate (for many reasons) it simply set the calculated soot mass to the field limit and then the regeneration starts. So don't trust on that number when you see those jumps. The question is: why the ECU forces the regen? It can be for fixed time limit reaching, for a fixed mileage limit reaching or of some other system failure. When something is working wrong in the DPF system, the ECU launches the regen very often because it no longer trusts the sensors. To avoid the risk of DPF self burning and fire.

Your case seems very complicated. Have you already asked to a dpf expert or to the vw service support?
I understand that replacing every component step by step is not the best way, but sometime it's the only thing we can do if we don't find a professional expert who can guide us.

[Billycool]

Thanks for the information.

I actually had someone come out today who does carbon cleans and DPF cleans. As the DPF was chemically cleaned a few weeks ago, I just had the carbon clean done. They use a diagnostics reader during the carbon clean to watch the live values and see if anything looks wrong.

DPF and DPF pressure sensor

The DPF pressure seemed a bit high at idle (20-25 hpa) and although revving to 2500rpm only raised it to 40 hpa (supposedly within limits), when under load driving, the hpa can jump up to 400+. So, the DPF sensor is recording high figures that would suggest a blocked DPF, even though it's had a chemical clean (the idle hpa is much the same as pre-clean). I need to test the DPF sensor plug voltages, just to make sure they are correct. I fitted a new plug when the other one melted and spliced in the wires. If the voltages are wrong or not being read correctly, that could be an issue.

EGR Valve & Cooler

Although the EGR valve was opening/closing as requested by the ECU, it was noted at being a bit "sluggish" (slow) to respond at it was possible that the airflow was also restricted by a gummed up EGR cooler - a common issue with this sort of mileage. The EGR could be full of crud and need a clean or replacement.

Oil consumption

All of the EA288 engined TDI's seem to use oil, particularly the 184 versions. Mine isn't actually that bad, so the whole loose piston rings and burning oil could be an issue but I'm not sure that's why the car is pushing up the measured soot levels.

Injectors

During the carbon clean the injector values are monitored and they show better efficiency post-clean. One of them appeared to over-fuelling and the other 3 were compensating. One was up to +1.97 and the others were -0.46, -0.57 and -1.01 to compensate. That needs further investigation as an overfuelling injector could mean unburnt fuel going into the DPF. No idea if the car would know this and whether it includes it in it's soot calculations.

Summary

I think it's hard to pinpoint one cause. Reading up on the forums, people who have had similar issues found that a new DPF solved a lot of problems. For the high oil burners, new piston rings helped. There is no singular answer. Fitting a new DPF is almost last resort, but if it's not a sensor or maybe the injector, then I may take the nuclear option and go for new DPF, new EGR and EGR cooler. They are all known to fail, clog up and cause issues. I plan to keep the car so can justify the expenditure as they would probably need some TLC in the future anyway. I just need to check the injector issue and check the DPF sensor wiring to make sure it isn't caused by that.

Either way, I need to get to the bottom of it. If anyone has any input, I'm all ears!

[admin]

Huge amount of details! Thanks for sharing.

In many cases we (in general) can't be sure if a value is within the specified range and considered ok or not. For example your diff pressure or the injected fuel. Without the design specs we don't have a real reference to evaluate, but sometimes comparing with the same engine of another car can give a useful feedback. Have you found some comparable data in the web regarding your engine?
The "normal" values for diff pressure should be quite easy to find and I remember that I recorded values of 400hPa in my logs without any engine issue (but always below 100k km).
For the injected quantity I have in my mind a max acceptable value of 2,00 mg/str but I don't remember where I've found it. I also remember that I checked the values in my old CRBC engine, at about 100k km, and they were all below 0,5 mg/str. But I'm still not sure if all TDIs have the same max values, maybe they depend on the injector brand/model.