DPF

[Andrija]

Hello,

I have a problem with DPF regeneration after remapping, Audi A5 35 tdi. I would like to point out that the original map was restored after 10 days but the problem remained the same. No errors are read from the diagnostic software. The EGR and EGR cooler and both pressure sensors were replaced.

Active regeneration takes too long and when it reaches the required temperature it drops after a maximum of 1 min (20-40 sec). I am attaching a graph made from the data that the VAGDPF app logs. The log is from 3 days, approximately 120 min is needed for regeneration to complete. Driving on an open road. When I take my foot off the gas pedal a little, the temperature drops immediately.

Also, the difference between the temperature before and after the DPF seems too big to me, an average of 150 degrees.

This has been going on for almost a year and since the problem started I have driven almost 25,000 km.

Has anyone had a similar problem or can you guess what is causing the ECU to reduce the temperature before the DPF.

[admin]

I don't have much experience on issues, but this kind of issue is the first time I see.

Basically the ECU controls the post injections and the EGR opening to regulate the gas temperature consequently. After that, the burning of the soot increases furthermore the temperature inside the filter, in fact when the soot level is low, the burning rate decreases drastically compared to the first part of the regeneration when the filter is full of soot.
If you don't see any error in the ECU log, it seems that the ECU acts as usual to manage the regeneration but something else in the system doesn't work as expected. It's quite impossible to identify the faulty component simply reading a graph, but maybe someone with the same issue can help you.

Have you already asked to a dpf expert?

[Andrija]

Thanks for the answer.

I've already visited 5-6 services but they only scan (vcds, odis,...) and when there are no errors I get the following instructions (different from each):
- buy a new DPF
- buy a new ECU
- everything is fine, you're making it up, just drive

I think they simply don't want to look for the problem because it obviously takes a lot of time to find it.

Next I'll remove the DPF and check if there's a crack because no one has done that because the pressure is within normal limits.

[admin]

Unfortunately, it's a common practice to follow the on board diagnostic only. If there aren't errors, the system works fine for them.

The expensive solution is to replace everything (but we know that sometimes also this strategy doesn't solve with these so complicated cars), the cheapest one would be to find someone who already faced and solved the same issue.

[Andrija]

Today I visited a service that is willing to look for the problem. I came when the car was in active regeneration, the values ​​of temp sensor 1 were unusual for them..... They re-adapted the pressure sensor, reset the DPF and performed a forced regeneration. The forced regeneration finished in 15 minutes and the car did not lower the temperature for the entire 15 minutes until it finished cleaning. It is strange that it will not do the same when it is in active regeneration, but in forced it will.

The agreement is to see how it will behave during the next regeneration, after which they will inspect the entire installation and all sensors.

The only similar example I found was caused by a damaged wire on the temp sensor.....

I will definitely report if there is any new news.

Thx admin

[admin]

It seems a professional analysis.
Good luck and thanks for sharing the results!