Urgent opinion/advice

[joksi]

Hi all!

Hopefully there is someone here that have experience and could help me.
My car is atm either starting , engine shaking and directly shutting off or it remains running but with practicslly no power at all. The car is an Audi A4 2.0 TDI with 180 000 km. Only known long time issue is increasing oil consumption (no visible leaks) during last couple of years.

So some background info. Maybe two months ago, first issue waa sudden error code about EGR low flow. It came and went away sporadically, then never came back again. During the same period the car started consuming much more fuel, and also started showing psrticulate warning light (which went off after driving as well ). This has since been sporadic but returning, however the last two weeks the car got noticeably more powerless and suddenly one trip started to turn on a bkinking warning light (glow plugs?) and lost like all power, together woth new errorcode turbo charger underboost. It happened almost every accelerarion after that.

Now i installed the DPF VAG app after searching info about the DPF warning initially, and noticed the following behaviour. The car seems to fo active regenerations like every 5-10km after it finishes one (from 100% to about 10%, anf 5-6g soot), the measured soot value rises from idle when driving normally to 25 and then the app sounds again (the calcukated value is low but jumps up). Also the differential pressure is from start att 300-500 on idle valur and while driving around 1000.
Finally the ash value is showing 0.13 l (not gram?)

What if anything can be said and suspected by all this?

[admin]

It seems a complicated issue.
What I can tell you is to don't fully trust on what your read from the app because those values can be altered by the ECU, if needed.
For example the sudden jump of the soot mass is the common clue of the ECU management: it can force the soot mass filling to 100% to immediately start the regeneration process, this can happen when you reach the maximum time or mileage limit between regenerations, or when there's a sensor fault. Or also for any other unexpected value that the ECU detects. Unfortunately we don't have the full specs of the DPF system, hence many evaluations are based on experience on the field shared by users, not on a real technical documentation.

Did you already visited a service center or maybe planned to go to? An experienced engineer has probably a more reliable answer for you than what the web can provide.
Sometime a simple sensor failure may create a big issue, only because the ECU can't be sure about what's really happening in the system, and for safety reasons it forces frequently regenerations to avoid the risk of fire. Replacing the sensor fixes the issue with few euro. I hope this is you case.

[joksi]

Hi!

First off, thanks for the reply!

Yes the car have been visiting the mechanic, however after getting it back (and a couple of hunred bucks poorer...) i feel like it isnt resolved. Well, the mechanic doesnt agree vecause the car now starts and runs prwtty good, however i try referrimg to the numbers and behaviours of this app. He said dont focus on trhat, just drive the car and enjoy... well, sure, i could try to ignorw the completely but whays harder to ignorw is the fact that the car itself seem to show that it still regenerates like in a loop (idle rpm at 1000, start stop deactivated and the fan runninh pretty much after each engine stop)
So this makes me watch this app, closely.

The only difference currently is that the pressure on idle seem to have lowered from about 200-250hpa to like 50-100hpa (with cold engine anyway). However thw rest is still the same, about 1000hpa while driving, the app sounding like every couple of kilomerers that ita regenerating again and again. The measured soot climbs up from 5-6g to about 25g in just a couole of kilometers.
Maybe even more strange, only way to lowwer the measured soot and finish a regenerstion is to stop and wait on idle! If i drive on the highway is either slowly rising or stabilizes around 25g (all the while thw calculated soot is much lower and increasing much slower and also decreasing faster)

I really dont undersyand whats happening.
The mechqnic said he tried to clean the dpf , and thhats the reason why engine runs normal now. Question is for how long with the above behaviour though....

[joksi]

Hi,

First, thanks for the reply!

I see. That doesnt sound so reassuring
I guess the strangest thing is wht a started regeneratiom cannot finish while driving on the highway, but whrn stopping on idle and waiting it out. On the highway the percentage at top does decrease, bit the measured sooy level either increases slowly or stabilizes arounf 25g. I have tried this jusy now, drove for about 30 min woth active regeneration and it got down to 2%, then i parked and idled to see if regeneration wpuld stop. Hpwrver it only stopped after like 10 min on idle, after the measirwf soot went down to like 5-6%. Then the app indicated that it was done, the rpm went down to normal.

Then i drove away again, and after 4 or.5 km the neasiref soot climbed upp to 22-23 g and rhe app jumped to 100% again and indicated yet another regeneration starting. I really cant get a grip of this bwhaviour....

Yes the car was at a mechanic, they did some kind of cleaning of the dpf, and the car could start and engine run smoothly again. Still its domething wrong, bwcause it continues to regenerate in a loop in the background....

[admin]

I let both your new messages because the contents are not identical, despite some parts are duplicated, but no problem.

How many kms did you do after the cleaning?
Reading other reports, I understood that the ECU is programmed with very very precautionary routines, this means that if it feels something wrong, it doesn't revert to a normal running just after a sensor replacement or dpf cleaning, it considers the issue solved after many kms or hours.

The only way to force it to immediately run in normal condition is using an adaptation command through the diagnostic software, but those adaptations are limited to some functions of the PDF system only.
I've seen issues solved after 1000km of driving.
Maybe the mechanic is right and you just need to drive for some hundred kms.

[joksi]

Sorry about the duplicate posts, i missed that it was moderated so i thought my first post never went through!

Well, I have driven about 500km since then. One can wait and hope....

Another recent observation which I guess is new, each morning I have tried to read the values with the ignition on just before I starr the engine, anf the app first reported DPF pressure differential -37hpa or -38hpa a couple of days, then switched to 15hpa yesterday and this morninh it showed 30hpa.... shoulf a correclt workinh DPF pressure sensor act like this or is it something unreliable with the app? I expect the value shoulf be 0hpa.

Another observation, like I said already, after stopping the car and idling the measureed soot value starts deceasing directly but if i start giving throttle (still on idle) slowly rising the RPM the measured soot starts climbing at about 1200rpm, but not on 1100.

Otherwise it takes about 10 min on idle before measurwd soot is down from 25g to 5,5g and the regeneration is finished. Thats the only.way for it to be able to finish.at all.