MOT exhaust emission fail

sweeper

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So, a while back my Viano started to smell diesely and one of the injectors was blowing by, so I decided to have all replaced as the mileage is 327000, it ran much better, smoother pickup and more power plus better mpg, well worth it then? Well, maybe not as it has just failed mot on high emissions, not that they are really high but the plate figure is really low at 0.1 compared to the R class which is 0.5 all this assuming I am looking in the right place, so if the plate value isn't there or can't be found the limit for my age of car is 1.5 and mine is coming in at 0.4, but due to the plate value being 0.1 it has failed.
The MOT station say put a new dpf, without any diagnostic work this seems a bit dodgy, so I am doing what should be done, taking it to Mercedes for a diagnostic, there are no fault codes and the lambda reading appears ok so what could the issue be, does it just need a good thrash or has the garage that fitted the injectors not put the codes in correctly, it runs great so i doubt it would make any difference with the closed loop control, could it be the dpf, if so what is wrong with it, the usual issue is that they block up but there's no evidence of that and it does get some good runs.

Anyone had experiences similar to this? what was the final outcome?
 

wongl

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I could be wrong, but when fitting new injectors, they need to be calibrated using Star Diganosis? Did you calibrate the new injectors installed?
 
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sweeper

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Thanks, you are correct and the specialist that changed them assured me he had done this, anyway the van has been into Mercedes who have done a full diagnostic check there were a couple of stored faults which were historic relating to the oxygen sensor but this was functioning correctly, it was removed and then replaced, no other issues found and the emissions test was passed with a reading of 0.01 compared to 0.4 previously, the MOT station have offered a retest but wont accept the Mercedes readings, he has however said that if it fails the emission test again he will pay for the MOT at Mercedes, it's in later today so will wait and see,
 
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sweeper

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So, get this, took it back for retest gave it a good run before to get it hot etc, and it failed again, So the garage did the retest again and again, eventually they got a pass. The problem is I want the vehicle right and have paid Mercedes a considerable sum to check it out and they say it is ok and I have a pass result to prove it. Obviously this leaves me with an issue, is there a problem or not? MB say no and it passed the test with flying colours MOT station say they shouldn't have to do more than two tests, I guess i'll worry about it next year.
 

artyman

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Is the MOT testing gear suspect?
 

markjay

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There's a long list of concoctions (and other treatments) that you can pour into the engine in an attempt to lower emissions enough to pass an MOT test. That, coupled with an 'Italian tuneup'...

Most are probably snake oil, but for what it costs, might be worth a shot?
 

mikrt

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And definitely use a different MOT testing station.
 
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sweeper

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Yes, I gave it a good thrash to clear it out, but should you have to? for me i'd rather know everything is ok, but in this instance the MOT station just say change the dpf and Mercedes say it's ok, guess where it's going for next years mot? I did wander if the new injectors were causing an issue with the fact the ecu will have adapted to the old worn ones and it's taking a while for the ecu to re adapt, I recall a few years ago having this issue when changing the gearbox oil in my old C230k, it took two months and a trip to europe to sort itself out with clunky gear changes and lumps after i'd stopped (to be honest i thought id broke it, particularly bad was 1st-2nd when cold) i guess its a wait and see, I will probably book it early for its next test and see if there is a problem, giving me a bit more time to sort it out.
 

M0HAO

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I went for MOT a week ago, for my 2013 Viano 2.2CDI (OM651 engine).
It failed for smoke test.

Test details were:
Test limit applied: 0.10 l/m
Mean Absorption coefficient: 0.14 l/m
Zero drift: 0.00 l/m
Test type applied: Turbo
Test result: Fail

That was a week ago. Then, I spent a week reading websites, MOT stuff, etc.
I went to the garage where I use to go, and I bought a bottle of Forte and spent an hour up and down on the motorway.
Then I got BP Ultimate Diesel (the expensive one), and a bottle of Redex Emissions Reducer, and went again to the motorway to run up and down in 4th and 5th, revs from 2k up to 4k.
Early today I removed the air filter too.

I came back to re-test today, a week after first test.
Re-Test details:
Test limit applied: 1.50 l/m
Mean Absorption coefficient: 0.14 l/m
Zero drift: 0.01 l/m
Test type applied: Fast Pass
Test result: Pass

I am happy because passed, but I am lost...
First point: Forte and Redex aditives, Ultimate diesel, air filter removed, motorway, are useless, results does not change.
Results were same; 0.14 l/m, but test type and limit were different.
Which one is correct?
 

Gazwould

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Looks like the manufacturers VIN plate smoke coefficient figure was applied in first test and a higher default figure disregarding the vin figure was applied in the second .
 

14emerc

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What I do know is that having the wrong engine oil can affect the test, as for the others ?
 

M0HAO

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Looks like the manufacturers VIN plate smoke coefficient figure was applied in first test and a higher default figure disregarding the vin figure was applied in the second .
Car´s plate says 0.1 inside a square.
So you meant first fail was correct, second pass not :(

Just trying to understand all this new MOT figures, thinking on next year...

having the wrong engine oil can affect the test

In my case, oil is Mercedes brand, synthetic, etc. best available.

Cheers
 

Gazwould

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The oil is a matter of opinion..


There is better other manufacturer oil specs out there than MB .


Yes first is correctly applied test .
 

zipdip

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Well I would use another garage for the next MOT,I am never sure if their equipment is always kept up to the mark,lets face it they get used alot,I wonder if they ever get serviced,with regard putting Forte or Red X in the tank what you need to do is put the whole bottle in a 1/4 of a tank of diesel but do it around a quiet industrial site because you will throw out vast amounts of black crap if your motor is bunged up,then put fresh diesel in give it a run and put it in for the test,also it is now important to get a MOT appointment and turn up and get it tested while still hot ,no more leaving the motor until they get round to doing it.
 

Phil1968

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Last year my work 2012 Vito 113CDI van that I'd had from new failed on emissions at 240,000 miles, diagnosed as needing a replacement DPF & cat. Got quoted a £6k bill to carry out the replacements :oops: My boss wasn't happy as the dealer did the MOT straight after carrying out a £600 service 😂 They ended up just scrapping the van (shame, as it still drove fine & didn't consume any oil) & bought me a new one instead.
 

tjamesbo

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Last year my work 2012 Vito 113CDI van that I'd had from new failed on emissions at 240,000 miles, diagnosed as needing a replacement DPF & cat. Got quoted a £6k bill to carry out the replacements :oops: My boss wasn't happy as the dealer did the MOT straight after carrying out a £600 service 😂 They ended up just scrapping the van (shame, as it still drove fine & didn't consume any oil) & bought me a new one instead.
shocking & scary
 

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