Om651 frequent DPF regen

[Cla2402]

Hello guys! So I have a 2014 CLA with the om651 engine and its driving me crazy. The dpf keeps regenerating every 60 miles or so.

So far I have replaced the DPF pressure sensor, thermostat and ECU software but it has made no difference. Car runs sweet, no knocks, no soot in exhaust tips, no fault codes etc.

I was told by a local indie all injectors need replacing. What do you think about this? Like I said, car has no issues at all, even cold starts are fine, how could they arrive at this conclusion? For the diagnosis they used xentry but did not pull the injectors etc...

Thanks for all your replies!

 

[mersum1es]

If some of the injector is under or overfueling, particulates are born, and filling DPF. I doubt all are bad. Usually when one goes duff, other are compensating and thus xentry values may go outside range.

Often DPF sensor pipes can be clogged, causing fault code/regen.

 

[Cla2402]

Thanks for the reply. The pipes to the sensor were also replaced. Is there a way of definitely telling via STAR that injectors are faulty or is the test bench the only definitive answer here?

 

[mersum1es]

ECU is measuring combustion via rpm, and adjusting injection timing trying to keep each cylinder 'power' on same level. If that correction values goes too high, injector is stated to be faulty. OF COURSE any other mechanical fault which has effect to combustion efficiency (for example low compression pressure), can cause similar thing. So bench test will be only 100% sure.

 

[Cla2402]

ECU is measuring combustion via rpm, and adjusting injection timing trying to keep each cylinder 'power' on same level. If that correction values goes too high, injector is stated to be faulty. OF COURSE any other mechanical fault which has effect to combustion efficiency (for example low compression pressure), can cause similar thing. So bench test will be only 100% sure.

Thanks for this info it is much appreciated. In my case at idle the corrections are out by no more than 3 rpm but usually within 1.5 rpm per cylinder according to the diagnostic tool. Is this fairly ok?

 

[Cla2402]

However when rapidly accelerating or decelerating the value can be up to 20rpm for a split second.

 

[mersum1es]

SDS says how much difference is allowed in smooth run test, but injectors have their own correction values and that gives hint about injector 'condition'.

 

[Cla2402]

Thanks. Next stop will probably be trying to clean the dpf and putting the injectors on a test bench.

 

[felloffajetski27]

did you sort this?

 

[Cla2402]

Hi, no unfortunately. Dpf has been removed and cleaned, new dpf pressure sensor was fitted, new thermostat, new software etc...yet the bloody dpf regens every 60-70 miles!

The car runs spot on, no warnings, starting problems etc... had it plugged on xentry 3 times in two different places and yeah you guessed it - no faults or indications something is wrong. It is actually driving me crazy

 

[Cla2402]

The fill rate of the dpf increases really quickly...yet at idle the pressure reads roughly around 5-6 millibars, regardless if the dpf is 20% or 80% full WTF

 

[mersum1es]

umm... it is not remapped, or adblue removed?

New DPF told to ecu (reset made)?

 

[Cla2402]

umm... it is not remapped, or adblue removed?

New DPF told to ecu (reset made)?

Not remapped and it does not have ad blue. Yes the reset was done twice on the dfp once in xentry ( did nothing) so then i tried with my launch tool and again nothing. I have attached pics of my dpf before cleaning. I assume the dpf is doing its job as the other side was clean even before chemical cleaning?

 

[Cla2402]

and here is a pic after having driven nearly 30 miles. At the start of the drive the soot was 0% as it was just after the dpf reset and clean. Why the ash content is 2.7g is beyond me as the system was cleaned and values fully reset to 0.00

 

[stressd]

It sounds like it thinks it’s full and runs a regen. Each time the soot burns off, it leaves behind some ash and that ash eventually builds up and clogs up the dpf. AFAIK, to get rid of the ash you have to open up the dpf (but I’m no expert). How did you clean the dpf?

 

[mersum1es]

All parameter except pressure are 'calculational', so ecu thinks it know ash content. How car starts regen; 1. calculated value reach limit, or 2. pressure sensor reading triggers level.

So it is calculation value (you said pressure difference is not rising)? Some mechanical fault would make sense like EGR leaking or boost like, which are causing heavy smoking and are filling the filter in real life.

 

[Cla2402]

Hello gents! Thanks for your replies. So the mystery deepens. The dpf values have been reset after a chemical solution clean. Regen intervals before the dpf clean were around 70 miles. After the dpf teach in, I have the following regen intervals:

202 miles, all motorway driving
251 miles, 50% motorway 50% city all cold starts etc...
166 miles all motorway

Ash is now calculated at 0.2 grams. Question is, why is there such a big difference between the regen distances? The motorway runs were more or less all identical in terms of speed, rpm, where the car was filled up etc...

I am going crazy here

 

[Cla2402]

So I processed the data I had and it seems that while driving (with very similar operating conditions) the fill rate over a motorway distance of 60 miles increased by 7% whereas on the latest occasion 60 miles on the motorway produced a fill rate of 38%. That to me is a huge difference in dpf fill rate. Both journeys were very similar, i.e no traffic, steady 70mph...car fully up to temp, shell v power diesel etc

Here are pics of the temp sensors under full load when the fill rate increased quickly

 

[sautah]

Have you confirmed the new pressure sensor is working correctly ? I would suggest looking at this again if you haven§t already.

Also if you have the correct san tool you should be able to see the reason for the last 16 Regens..... Might shed some light on things.

 

[The-nuke]

Have you confirmed the new pressure sensor is working correctly ? I would suggest looking at this again if you haven§t already.

Also if you have the correct san tool you should be able to see the reason for the last 16 Regens..... Might shed some light on things.

What I would do is take it to Jimmy at O,Rileys Auto's. Has a Youtube channel. DPF Guru Might be worth trip out because you don't want to damage DPF very expensive.