Help please! - 2021 New GLA DPF regeneration problems/issues... reject the car?

[roryg]

Hello

Hoping someone can help with an issue I've got as the dealership want to wash their hands.

I bought a new GLA 220d in the middle of May and a week later my wife noticed a very strong burning smell coming from the engine compartment after the school run (a 32 mile round trip on mainly fast-flowing A roads). Emailed the dealer, got told to keep our eye on it.

A week later I noticed the same thing, a really strong burning smell and excessive heat radiation from the engine. 45 minutes after arriving home the bonnet was still hot to touch.
Should mention that we normally average around 56-60mpg on the school run but on both those days the average was around 40-42mpg. When I got to school it was 61mpg so the return trip I got only 23mpg!

I called the dealer and he told me to bring it in for a diagnostics. This showed that a DPF regen was attempted on both those days but failed to complete because the ignition was switched off (first time after 18 minutes, second time after 23 minutes). When I bought the car no mention was made of a DPF filer or that it needed regular cleaning.
However, I did a bit of research and it seems the process should normally take between 5-10 minutes to complete.
Begs the question why mine failed twice and resulted in such reduced fuel economy.

There were other issues, dashboard vibration, steering wheel 'clicking', failure to engage 'glide' mode so the garage took it in and held onto it for almost two weeks.
Got it back two days ago and the 'glide' is now working but all the other issues remain and now there is more vibration and excessive play on the steering wheel.

I met with the General Manager and a technician and he gave me a Mercedes technical document on the DPF and explained that even though the process hadn't completed it most likely had blown out most of the soot. That put my mind at rest, sort of. I asked the technical guy how long a regen process should take, he said 20-30 minutes. Seemed excessive, but I left it at that. However, when I got home I read the technical document that states "The regeneration process takes a few minutes and depends on..."
A few minutes, not 20-30 minutes. Alarm bells ringing now so I email the technician and ask why he said 20-30 when Mercedes say "a few".

He got back to me and said there is no set limit for a regen process and sent me a document explaining the short distance trips process. Pointless really because my trips are over 30 miles on mainly A-roads at speeds of 55-65mph so the info he sent is not applicable to my circumstances.

Surely a 32 mile round trip on A-roads in summer should be enough to complete a DPF regen cycle? I have a gut feeling that there is a fault in the system somewhere but they are denying it because there are no diagnostic errors pointing to a problem. They say it is functioning as intended, which I dispute.

I think the process is perhaps completing in a "few" minutes but the system doesn't recognise this and so continues to inject fuel into the exhaust system when it really shouldn't, causing over-heating and the atrocious burning smell on arrival back home, combined with the extremely low fuel aconomy experienced during the regen attempt. The dealership are discounting this possibility, even though the regen process continued for 23 minutes.

I did some calculations too. I was interested to find out how much fuel was injected into the exhaust system to heat it up sufficiently to burn off the accumulated soot.
It turn out that the trip to school (16 miles) used 1.2 litres of fuel and the trip back used 3.2 litres... so the DPF regen process used 2 litres of diesel (£2.50), took 23 minutes and still didn't complete! It doesn't add up to me, but I'm no expert. If this regen process happens roughtly every 300 miles as Mercedes say, then over 3 litres of every 43-litre tankful (7.5% of the tank) is being 'wasted' - basically to heat up the exhaust system.

I think these figures prove that there is a fault and I'm within my rights to reject this car (still within 30 days as the garage had it for 2 weeks).

I spoke to my brother who has had a diesel Skoda Yeti from new (2015) and has never experienced issues with the DPF regen, no burning, no noticeable reduction in fuel economy etc. I'm assuming this is how it should work and I've been unlucky to get a lemon.

I would be grateful for any opinions or insights. Does this seem totally unreasonable? Should I even notice the burning, is it over-heating, why the excessive use of fuel? So many questions the dealership seem incapable of answering.

Obviously I'm very unhappy with my GLA ownership and really want to reject it. We chose Mercedes because our previous car (a 2012 A-Class) provided 9 years of trouble-free motoring and we never noticed any DPF issues. It just worked and I expected the GLA to do likewise.

Thanks for reading and thanks for your help.

RoryG

 

[Blobcat]

The emissions equipment has become more onerous on Euro 6 - DPF burn off is a regular smelly issue. I never noticed on my W213 220d as I was doing 180 mile journeys with it, I did used to get clouds of smoke and smell from my VW Caravelle when it did a regen though.
There's quite a few Euro 6 Diesel owners on here so you should get some good advice

 

[roryg]

Thanks Blobcat - new to this DPF stuff, was just hoping it would all happen behind-the-scenes with no drama... Hasn't turned out that way!

 

[Binnedit]

I'm not well up on DPF's & regen cycles etc, however I would suggest 1 month from new, whilst doing those sorts of journeys, that the DPF shouldn't have a sufficient build up of soot to require a regen in the first place?

I know the CATS can smell a bit from new, for a short while.

Sounds very odd to me, but could be wrong.

If you are not getting any joy with the Managers at the Dealership, I would ask for an appointment with the Dealer Principal / Brand Manager

 

[roryg]

Apparently every 500km (300 miles) is about normal. Mine took about 450 miles to the 1st one probably because of A-road driving and no town stuff.
Yep, maybe I need to go higher. Thanks for advice.

 

[mattkh]

I bought a new GLA 220d in the middle of May
I spoke to my brother who has had a diesel Skoda Yeti from new (2015)

We chose Mercedes because our previous car (a 2012 A-Class)

RoryG

Thank you very much for the detailed post. Most educational.
What was the mileage when you bought the GLA..?
Was the Skoda the 1.9 TDI engine..?
Which engine was it on the 2012 A-Class..?

 

[Nickhgard]

We've got a 2020 Vito for work which only does short stop start journeys (local delivery vehicle). The Dpf tend to regen in between deliveries and we've had no trouble in 12k miles. If it starts regenning just before its turned off it will resume once started up again.
DPF will be an issue with modern diesels due to emissions. Unless you're doing lots of long journeys petrol is always a better alternative

Sent from my VOG-L09 using Tapatalk

 

[roryg]

Thank you very much for the detailed post. Most educational.
What was the mileage when you bought the GLA..?
Was the Skoda the 1.9 TDI engine..?
Which engine was it on the 2012 A-Class..?

No problem - mileage was about 10, got it new. Not sure about the Skoda, brother not about right now.
The A-Class was the old style MPV type (W169) - it was the A160 BlueEfficiency diesel. Never a single problem with it!

 

[roryg]

We've got a 2020 Vito for work which only does short stop start journeys (local delivery vehicle). The Dpf tend to regen in between deliveries and we've had no trouble in 12k miles. If it starts regenning just before its turned off it will resume once started up again.
DPF will be an issue with modern diesels due to emissions. Unless you're doing lots of long journeys petrol is always a better alternative

Sent from my VOG-L09 using Tapatalk

Yeah, this is my dilemma - we are doing 2x32 mile journeys every day - I don't consider that 'short distance' aka town driving - so the DPF regen should complete, I would have though, but it doesn't... and it wastes a LOT of diesel - 2 litres on one failed attempt. Can't be right surely?

 

[V6Matty]

32 miles is probably right in the middle of the regen when things are at there hottest which would explain the smell when you arrive home and shut off. I would say the only thing for you to do is when to know it’s doing a regen, keep driving until it’s finished and then go home, what your doing now is getting to maybe 30% filled after the failed process meaning it will happen earlier and earlier until the car can’t do it itself and had to be forced.
Really good post but I think the regen bit isn’t actually an issue but just a real pain for your very specific driving style, you could ask for the dealer to ensure it had the latest update as I bet they haven’t tried that yet, they don’t like doing updates if they can help it as it take up space on a ramp and can’t do anything else to the car at the same time, so wasted time unfortunately

 

[Jim2]

The thing about regens is that until you become aware of what's going on under the bonnet, they can be scary....burning smell, bonnet hot to the touch, higher rev's etc. Use to frighten the life out of my Wife when she first experienced it in her Skoda Superb. Now, it no problem for her. In my 2014 E class, I regularly check out the DPF with my iCarsoft CroPro, and so far, its behaving beautifully. Most of my driving is up and down steep hills , and that keeps it in good working order. Short start / stop driving is the death knell of DPF's... in any make of car. If in doubt when buying a car, go for the petrol version, and save yourself a lot if headaches ( not to mention cash...... There are certain conditions that have to be met to enable a trgen to take place...and you could be hitting the "wrong" times.....its possible that you will cover 50 or a 100 Miles, but only in the last 5 or 10 miles will the regen starts and it wont have time to finish the process. So it will have to begin again. Its long been a pet beef of mine, that with all the high tech warning lights and icons, they did not install in the factory a regen indicator icon on the dash. Its possible to rig a warning light from the heated rear screen ( it is activated during a regen ) if you rreally wanted to know when a regen is taking place.

 

[mattkh]

Its possible to rig a warning light from the heated rear screen ( it is activated during a regen ) if you rreally wanted to know when a regen is taking place.

Interesting, but why heat the rear windscreen during a regen is baffling..?

 

[Jim2]

Interesting, but why heat the rear windscreen during a regen is baffling..?

The rear screen and door mirrors are both activated during a regen, which increases the electric demand, on the alternator, which increases the load on the engine, in turn increases the engine temperature to facillate the regen. Thats a bit if a roundabout explanation, but it's what actually happens. Search for a poster named MrGreedy on this forum. He has installed a regen warning light in his MB, and given very clear step by step instructions on exactly how he did it, so Kudos to him.

 

[Tony Dyson]

The rear screen and door mirrors are both activated during a regen, which increases the electric demand, on the alternator, which increases the load on the engine, in turn increases the engine temperature to facillate the regen. Thats a bit if a roundabout explanation, but it's what actually happens. Search for a poster named MrGreedy on this forum. He has installed a regen warning light in his MB, and given very clear step by step instructions on exactly how he did it, so Kudos to him.

I'm probably mistaken, but I thought @Mr Greedy reposted a mod by AN Other claiming this to be a fix for a regen indicator and he was planning to install? I recall I called it mythical at the time and have since tested it on my 2014 OM 651 and found it to be so, now that's not to say that other models, newer or older may use other consumers to increase the load on the alternator, what I found on mine is that it uses the glow plugs, the following is an excerpt from a MB OM651 System Description doc;

Diesel particulate filter glowing

Diesel particulate filter (DPF) glowing is only
performed during DPF regeneration to increase the
load and stabilize combustion.

 

[Jason63]

I think your DPF problem is this:

Unless you do a 45 min motorway run (which burns the soot off nicely, and without a forced regen) then you will typically need a DPF regen every 300 to 500 miles.
A regen won't start until everything is fully up to temperature, engine and exhaust.
A modern efficient diesel won't get fully up to temperature for at least 10 miles.
A small regen, holding an optimum speed probably will only take 5 mins.
If the DPF has got clogged then the regen period will continue until the exhaust back pressure reaches the target level, could be quite a bit longer.
The regen will pause if for example you slow down or stop - extending the regen period even more.
If the regen fails to complete then one will be scheduled for the next journey....and the cycle repeats...

I think your 16 mile journey (each way) is, unfortunately, a worst case scenario for a DPF regen on this vehicle. Other cars (makes, models) may get up to temperature quicker, do more regular regens, have DPFs that filter less soot.

What I'd do is go for an hour drive on a motorway. That should sort out a full DPF regen. Then see how the car performs after that and take it from there.

 

[malcolm E53 AMG]

The DPF pressure sensor (situated in the exhaust) measures the back pressure created as the DPF fills with soot and initiates a regeneration when required. The DPF regeneration does involve a lot of heat due to extra fuel being injected into the exhaust to burn the soot off and the process on my E350cdi lasts about 15 minutes (10 miles) in duration. Your motoring is ideal for a Diesel engine and the DPF regeneration process - problems usually set in with low mileage users due to not getting the engine up to maximum running temperature.
It appears from your description of the problem that the back pressure sensor in the exhaust is faulty, it may be an intermittent fault and when checked by the dealer hadn’t thrown up a code. A faulty thermostat can also cause problems (not allowing the engine to reach optimal operating temperature) so this is also something to watch out for.
I’m not enthralled with EU6 diesels and won’t be buying one to replace my EU5 E350cdi they are far too complicated nowadays so I’m changing back to petrol.

 

[roryg]

32 miles is probably right in the middle of the regen when things are at there hottest which would explain the smell when you arrive home and shut off. I would say the only thing for you to do is when to know it’s doing a regen, keep driving until it’s finished and then go home, what your doing now is getting to maybe 30% filled after the failed process meaning it will happen earlier and earlier until the car can’t do it itself and had to be forced.
Really good post but I think the regen bit isn’t actually an issue but just a real pain for your very specific driving style, you could ask for the dealer to ensure it had the latest update as I bet they haven’t tried that yet, they don’t like doing updates if they can help it as it take up space on a ramp and can’t do anything else to the car at the same time, so wasted time unfortunately

I think your DPF problem is this:

Unless you do a 45 min motorway run (which burns the soot off nicely, and without a forced regen) then you will typically need a DPF regen every 300 to 500 miles.
A regen won't start until everything is fully up to temperature, engine and exhaust.
A modern efficient diesel won't get fully up to temperature for at least 10 miles.
A small regen, holding an optimum speed probably will only take 5 mins.
If the DPF has got clogged then the regen period will continue until the exhaust back pressure reaches the target level, could be quite a bit longer.
The regen will pause if for example you slow down or stop - extending the regen period even more.
If the regen fails to complete then one will be scheduled for the next journey....and the cycle repeats...

I think your 16 mile journey (each way) is, unfortunately, a worst case scenario for a DPF regen on this vehicle. Other cars (makes, models) may get up to temperature quicker, do more regular regens, have DPFs that filter less soot.

What I'd do is go for an hour drive on a motorway. That should sort out a full DPF regen. Then see how the car performs after that and take it from there.

Thanks for the info, very interesting.
However, after both failed regens, it wasn't scheduled for the next run - I waited another week before there was any sign of a regen.
Surely if I'm driving 16 miles to school the engine should get up to temperature than, on the way back, a 25 minute journey along mainly A-roads at speeds of 55-70 should be enough to complete the regen.
First one said it failed after 18 minutes, the second after 23 minutes. Surely 23 minutes on A-roads should be enough to complete a regen?! If not, then the car really isn't fit for purpose. I'm not a town driver, and I'm not a motorway driver, I'm in the middle. However, when buying the car, not mention was even made about what type of driving I do. I went for a diesel for the economy and because I had 9 years good experience with my old A-Class. If I was made aware of the DPF and it's need to regen every 300 miles or so, wasting litres of fuel each time, I'd have gone with the petrol one.
I just think there is a problem with the regen process on my car as it should complete within 23 minutes and, if it doesn't, it should re-schedule for the next run - but it does neither.
Could it be a faulty sensor - the regen does take place but it fails to recognise this and continues to unnecessarily pump fuel into the exhaust system, effectively over-heating the whole system because it's not actually required because the regen finished 15 minutes earlier?
The dealer ran diagnostics and found no problems but that isn't to say the diagnostics are correct.
They won't let me reject the car until they confirm there is a problem but their diagnostics tell them there isn't a problem so looks like I'm stuck with, at best, an unsuitable new car, at worst, a faulty new car.
Wish I'd never bought it and gone with the Skoda Kamiq but the wife wanted another Merc! What was I to do?!

 

[roryg]

The DPF pressure sensor (situated in the exhaust) measures the back pressure created as the DPF fills with soot and initiates a regeneration when required. The DPF regeneration does involve a lot of heat due to extra fuel being injected into the exhaust to burn the soot off and the process on my E350cdi lasts about 15 minutes (10 miles) in duration. Your motoring is ideal for a Diesel engine and the DPF regeneration process - problems usually set in with low mileage users due to not getting the engine up to maximum running temperature.
It appears from your description of the problem that the back pressure sensor in the exhaust is faulty, it may be an intermittent fault and when checked by the dealer hadn’t thrown up a code. A faulty thermostat can also cause problems (not allowing the engine to reach optimal operating temperature) so this is also something to watch out for.
I’m not enthralled with EU6 diesels and won’t be buying one to replace my EU5 E350cdi they are far too complicated nowadays so I’m changing back to petrol.

Thanks for the info - maybe get the dealer to check the sensor.
Like you, my next car won't be a diesel - but I've got a long time to wait having just bought this one. Big mistake methinks...

 

[roryg]

Big question is, can I insist it is faulty because it is not completing a regen? Even having 18 and 23 minutes to do so?
MB's own technical info on the DPF states a 'few' minutes - won't that help my case?! Just got a nagging feeling that there is an underlying problem which may cause serious issues down the line - not what I expect from a new car.

 

[richlumb]

@roryg can I ask where you fill up for diesel ?