DPF power issue - limp mode

MBWill

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So a few weeks ago I began noticing my car would struggle to accelerate, when going from say 20 to 30, it would take a good 10 seconds or more to increase speed by 10mph.

Even in sports mode, it's exactly the same.

This issue was intermittent, recently it had become recurring, and the other day happened just before I was about to drive up a steep hill, I had my foot flat to the floor doing 70 on approach to the hill (it's a hill on a fast road), foot flat down all the way to the top, and at the top I was only doing 35.

Another issue is it feels as if the gears are holding the car back, it will change, try to increase speed, but it won't change gear so you can feel the car being restrained, almost as if it's on a speed limiter - which it isn't.

After thinking it may be the EGR, MAF or the turbo not working I took it to my local garage who connected it to their OBD scanner, the only error that came up was something about DPF regeneration not taking place, the engine management light now comes on every so often, but far more often than it used to.

Yesterday after visiting my mechanic I went for a drive to try and perform a DPF Regen burn, initially for the first 5 minutes the car performed as it should, with no issues, then I had to slow down due to a slow moving vehicle in front, the minute I applied the brake the engine warning light came on and the car went back into limp mode where it really struggles to accelerate and loses power on slight gradients.

I took the car for a drive, doing between 30 and 60 miles an hour, with it revving between 2,500 and 3,000 RPM almost the entire time, I probably spent over an hour doing this, my question is this.

The exhaust, although hot, did not appear super hot, like it's supposed to (apparently reaching around 600 degrees when performing a burn), there was no smell of ash and no excessive smoke.

Is this the correct method for 'forcing' a regen? Is there any way to know it's taking place, other than hooking it up to an OBD with a live data feed capability?

Additionally, how will I know the process is "Complete" so to speak, and that a sufficient amount has been removed?

I was told that should I continue to drive the vehicle for short journeys the DPF will become fully blocked and the vehicle will have serious power issues, as it is at the minute trying to overtake lorries on dual carriageways is a struggle, taking a good 20 seconds to pass them on full throttle.

I have bought some DPF cleaner, so will be using that as well as repeating the process again tonight.

The car does seem to accelerate from 0-40 better, however once you go past 40 it then becomes slower to accelerate, the whole time the EML (Engine Management Light) is on, steady amber.

Thanks in advance.
 

400ixl

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I would get the codes re-read. There can be a number of things that stop a regen from being performed. For example the temperature sensors for the exhaust and turbo.

With the fault logged if it is one which stops the regen it will just not happen and will continue to fill and block the DPF causing bigger problems, potentially having to remove the DPF for a manual clean out.

Get it on STAR at a local indie who should be able to read the codes and see what level the DPF is currently at and whether it is in a state to try to regen.
 

KennyN

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The car will only do an automatic DPF regen if it thinks the filter is full , it may be full but if the sensors dont see it as being so then it will not perform the proper cleaning cycle.

When mine does its cycle the cooling fan runs and i can feel the heat from under the car as the exhaust is super heated to clear out the filter , the exhaust also sounds hot if that makes any sense. On the CLS there is no indication displayed that the car is about to / is doing or has completed the cleaning cycle.

So , as a previously stated , get a proper diagnostic check done by someone with the pukka diagnostic gear.

Kenny
 

alex cnwell

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Mine had the same problem and was so full it could not regen, i had only had the car a few days (w203). my main cause was the thermostat and the dpf sensor . i unclipped the dpf sensor and bought a can of silver hook dpf cleaner off eBay for 9.00 and put the tube down the wider pipe (there are 2)and took the car for a hard run after fitting stat and new bosch sensor, i used my icarsoft mb11 to then force a regeneration and got the values down from 388% to 11%.. it now regens even on short runs if up to temp. there can be no issues with the car at all as this will stop a regeneration .
 
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MBWill

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I would get the codes re-read. There can be a number of things that stop a regen from being performed. For example the temperature sensors for the exhaust and turbo.

With the fault logged if it is one which stops the regen it will just not happen and will continue to fill and block the DPF causing bigger problems, potentially having to remove the DPF for a manual clean out.

Get it on STAR at a local indie who should be able to read the codes and see what level the DPF is currently at and whether it is in a state to try to regen.

I'm not sure what scanner the guy used yesterday, but it was quite expensive looking and looked a decent bit of kit, full on tablet style handheld touchscreen.

The only error that came up was DPF regen not performed, something about cycle, can't remember the exact error message, he cleared that code and then scanned again and no further error codes came up, in which case what would taking it to an indie with a STAR do?

If a scanner can read it to pick up the DPF error code, i'm not sure why it would miss other error codes that only a STAR system would pick up on.

I am considering just biting the bullet and taking it to a Halfords and getting them to perform a DPF Deep clean for a cost of £85.00, I need this car to be working properly before I go back to work on the 4th, and can't keep to-ing and fro-ing to a local indie every time I need to get the car scanned to have the codes read.

I would consider taking the DPF out and cleaning it by hand, however I am no mechanic and my mate who is an (almost fully) qualified mechanic has never done a DPF clean manually on a Mercedes before so is reluctant to do so.

Not trying to be argumentative but as i'm sure you can appreciate I can't keep taking it back to a garage and asking to use their machine to read the codes for free, would be taking liberties.

Would using a bottle of DPF cleaner sort this out, obviously emptying the whole bottle in and then adding diesel immediately afterwards.

In other words, with DPF cleaner added will it have any effect if a DPF regen isn't performed, as the solution is flowing through the DPF system?
 

Wighty

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I would have thought it's worth a drive to a decent Merc Indy with Star, or even MB , especially if you are going to pay for a forced regen (again without Star ) . I understand that Star can "interrogate" things a lot more deeply than other non MB systems . Maybe your car doesn't need a forced regen ??
 
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MBWill

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I would have thought it's worth a drive to a decent Merc Indy with Star, or even MB , especially if you are going to pay for a forced regen (again without Star ) . I understand that Star can "interrogate" things a lot more deeply than other non MB systems . Maybe your car doesn't need a forced regen ??
I thought STAR was just a diagnostics kit, can it actually physically force the car into performing a regen there and then once connected? From what I understand it just gives the instructions on how to perform a clean once the STAR system is connected to the car.

Also, is 2,500-3,000 RPM sufficient enough for a clean?

I tried to go at about 50mph yesterday in 2nd/3rd gear but unfortunately my car has what I suspect is a safety limiter, the minute you shift down the revs do not go above 3,000 RPM and the car forces itself to slow down to match the top speed of the gear you've selected, unlike a normal car whereby if you downshifted from 5th to 3rd at 50 miles an hour the revs would just go through the roof.
 

malcolm E53 AMG

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You may have a problem with the pressure differential sensors fore and aft of the DPF you will need to plug into STAR to verify a generic code reader probably wouldn’t pick this up and yes STAR can force a regen and that is all the engine may need hopefully, find a good local Indepenent that’s the wayI would go
 

Wighty

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As Malcom says ^ . Good Merc Indy needed who understands these systems . I'm in Essex so I don't know any Kent Indys . Hopefully someone will chime in , they have been recommended in the past . The MB owners club does have a specialist/Indy finder
 

400ixl

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Yes, STAR can force a regen, however, there needs to be no codes stopping this and also the ECU software needs to be up to date or it may refuse to do it.

As mentioned, there are acceptable ranges between the various sensors that can cause a regen not to occur.
 

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KennyN

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When you see a printout of a full STAR diagnostic check then you can see what it can really do and how deep it goes, i believe it can "ping" all the sensors and modules, check their functionality and readings.

There should also be an error log it can access to check previous faults / codes which should assist in finding the root cause of the problem.

You may get a DPF clean done at Halfords and it may cure your present dilemma but once the filter reaches its full condition again . which it will , then you will be back to square one.

No point throwing good money after bad , best get the car to someone who knows the brand and has the proper equipment to test it.

Just a thought , dont you have Mobilo breakdown cover as the car is just over three years old ? If so give them a call and the MB tech will have the equipment to run a diagnostic check and point you in the right direction.

Kenny
 
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MBWill

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When you see a printout of a full STAR diagnostic check then you can see what it can really do and how deep it goes, i believe it can "ping" all the sensors and modules, check their functionality and readings.

There should also be an error log it can access to check previous faults / codes which should assist in finding the root cause of the problem.

You may get a DPF clean done at Halfords and it may cure your present dilemma but once the filter reaches its full condition again . which it will , then you will be back to square one.

No point throwing good money after bad , best get the car to someone who knows the brand and has the proper equipment to test it.

Just a thought , dont you have Mobilo breakdown cover as the car is just over three years old ? If so give them a call and the MB tech will have the equipment to run a diagnostic check and point you in the right direction.

Kenny

I've had a lot of people ask me that question, the answer is no.

The car was bought second hand in September of 2016 from a Bristol Street Motors dealer in Durham (Newcastle way), on a finance agreement through Barclays, the finance was paid off in full about a month and a half ago, at no point was I ever offered any mobilio service plan, up until I asked the question on here of what it was, I had no idea what it was or that it even existed.

The only care plan i've looked at purchasing and even considered is the Mercedes one, however at my mileage (approx 30,000 a year) the price is £50 a month, or £600 a year, now my last two services have cost me a total of about £400, fully inclusive of parts, given that it doesn't even seem a courtesy car is included in the price of £50 a month, and partly due to my age and not being insured on a permanent basis to drive any other vehicle third party, I see no point at this present time in joining the plan.

Are we sure that no DPF regeneration will take place with the engine management light on?

What I find odd, when I start the car it drives fine, even with the engine management light on for the first 5 minutes, then it's almost like a switch, it instantly flips and then churns into limp mode, every time.

Starting to think my only realistic option is to have the DPF deep cleaned (either flushed through or removed and cleaned - at a horrendous labour cost), I can't regenerate it on the move as from what i've read the EML has to be off, now when it was turned off yesterday by the mechanic with his ODB tool, it then came straight back on within 5 minutes, so no opportunity to conduct a DPF regen.

I've emptied a bottle of Wynn's DPF cleaner into the vehicle and it hasn't made any difference - whether or not it should if the EML is still on, I'm not sure.

Either that or it isn't the DPF itself, and a DPF sensor, or oxygen sensor has gone kaput.

One thing I can say for sure though..... my next car will run on Petrol!
 

KennyN

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Mobilo is MB`s breakdown cover , your car will automatically be covered ,FOC, if it has a full MB service history and as the car has just turned three years old i figured that it would have been serviced by MB (or at least by a reputable independent who can update the history with the factory) to keep the manufacturers warranty intact.

Generally speaking , if you are doing 30k per year then there should be no issues with the car doing its regen process as it will be up to temp regularly so my money would be on a sensor , but as to which one then it is back to the diagnostics again i am afraid.

Kenny
 

alex cnwell

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It could be the soot content is just to high to do a regen, start with the cheapest option first, find your dpf sensor (probably on the rear of your airbox) and buy 1 can of dpf cleaner it comes with a line attached to go down the fat dpf pipe. follow the instructions on the can , its an aerosol and literally is a 5 minute job. take for a good run at 2-2.5 rpm . then get the light turned off mine went off on its own after a few more start ups.
 

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I've had a lot of people ask me that question, the answer is no.

The car was bought second hand in September of 2016 from a Bristol Street Motors dealer in Durham (Newcastle way), on a finance agreement through Barclays, the finance was paid off in full about a month and a half ago, at no point was I ever offered any mobilio service plan, up until I asked the question on here of what it was, I had no idea what it was or that it even existed.

The only care plan i've looked at purchasing and even considered is the Mercedes one, however at my mileage (approx 30,000 a year) the price is £50 a month, or £600 a year, now my last two services have cost me a total of about £400, fully inclusive of parts, given that it doesn't even seem a courtesy car is included in the price of £50 a month, and partly due to my age and not being insured on a permanent basis to drive any other vehicle third party, I see no point at this present time in joining the plan.

Are we sure that no DPF regeneration will take place with the engine management light on?

What I find odd, when I start the car it drives fine, even with the engine management light on for the first 5 minutes, then it's almost like a switch, it instantly flips and then churns into limp mode, every time.

Starting to think my only realistic option is to have the DPF deep cleaned (either flushed through or removed and cleaned - at a horrendous labour cost), I can't regenerate it on the move as from what i've read the EML has to be off, now when it was turned off yesterday by the mechanic with his ODB tool, it then came straight back on within 5 minutes, so no opportunity to conduct a DPF regen.

I've emptied a bottle of Wynn's DPF cleaner into the vehicle and it hasn't made any difference - whether or not it should if the EML is still on, I'm not sure.

Either that or it isn't the DPF itself, and a DPF sensor, or oxygen sensor has gone kaput.

One thing I can say for sure though..... my next car will run on Petrol!
Why do you still mention the horrendous cost of a dpf removal and cleaning . You can go round in circles all day guessing things , fair enough if the guess is cheap and easy and you don't mind doing it . BUT YOU NEED TO GET IT ON STAR OTHERWISE YOU MAY BE WASTING YOUR MONEY !!!!!
 

EXMERCTECH

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Any engine related fault will stop the DPF from regenerating.
You need to get a Mercedes Star Diagnosis check.
It could be something else not necessary a DPF fault.
 
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MBWill

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Why do you still mention the horrendous cost of a dpf removal and cleaning . You can go round in circles all day guessing things , fair enough if the guess is cheap and easy and you don't mind doing it . BUT YOU NEED TO GET IT ON STAR OTHERWISE YOU MAY BE WASTING YOUR MONEY !!!!!

This is my next port of call, I plan on getting it looked at on the STAR system, Merc want £120 just to diagnose the issue, no thanks.

Planning to take it to one of my local indies, whenever they are next open, bearing in mind it's the xmas holiday period so most places will be closed for the next few days.

I appreciate all the replies, I would clean the DPF myself as someone mentioned earlier with a can of spray cleaner, but i'm no mechanic and frankly the thought of fiddling with an engine and it's components terrifies me, I would happily change a wheel or an air filter but nothing more than that!
 

Wighty

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This is my next port of call, I plan on getting it looked at on the STAR system, Merc want £120 just to diagnose the issue, no thanks.

Planning to take it to one of my local indies, whenever they are next open, bearing in mind it's the xmas holiday period so most places will be closed for the next few days.

I appreciate all the replies, I would clean the DPF myself as someone mentioned earlier with a can of spray cleaner, but i'm no mechanic and frankly the thought of fiddling with an engine and it's components terrifies me, I would happily change a wheel or an air filter but nothing more than that!
A good Indy is the way to go ....good luck with it all
 

Botus

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I thought STAR was just a diagnostics kit, can it actually physically force the car into performing a regen there and then once connected?


any decent diagnostics kit can enable a forced regen cycle

a car driven correctly will never play up

one abused round town and never exercised on the open road, just gets worse and worse, by the time most owners decide it needs the dealership the abuse is too much for the DPF to cope

once a week 20 mile run at 80 mph and 2500 rpm. if you spend time doing 2 mile runs to school and then commuting in traffic make it 3 times a week
 


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