MOT Failure CO 6.14

[tesla6518]

OK I know this has been covered numerous times, But I have never seen readings this high
garage says Lambda sensor, however I pointed out that they changed it on the last MOT and the car has only done 10k (Coronavirus). No codes, no MIL results as below. all help/suggestions welcome.

2009 CLC180K (W203)

Fast idle test
manual check pass

CO 6.14
HC 175
Lambda 0.828

Second fast idle test
manual check pass
CO 6.69
HC 311
Lambda 0.811

Natural idle test

CO 6.47

 

[John Laidlaw]

Does seem extremely high, making me question the equipment used to check it! Not sure why they made the Lambda comment really, I've cut and pasted from DVLA below. Someone cleverer than I will give a greater insight I'm sure...
"The emissions limits to be met are specified for both the fast and normal idle tests. At fast idle, CO must be at or less than 0.2%, HC at or less than 200 parts per million (ppm), and the lambda value(1) must be between 0.97 and 1.03. At normal idle, CO must be at or less than 0.3%."

 

[joderest]

My 2003 ml270 just passed its MOT with a reading of 0.49
The max it could be is 0.8.
I did reduce emission by fitting an oil catch can.
The tester did state that the rules are going to get harder as the government wanting older polluting vehicles off the road.

 

[sonic]

This is my wife 2010 SLK200K 1800cc M271 engine, yours might be the earlier engine.

Fast idle.2620 rpm
CO 0.00
HC 5
Lambda 1.002

Natural Idle test
Engine Speed 760 rpm
CO 0.00%

 

[tesla6518]

OK people I hope this post helps anyone in the same position. I had the car brought home and decided to do some checks myself. firstly I ordered a new Bosch pre-cat Lambda sensor. Jacked the car up and removed the plug, and no need to guess, yes oil in the connector, the same with the after cat lambda sensor. went up top and checked ECU plug a smidging of oil. straight away ordered new Camshaft position solenoids (magnets) from Autodoc. £102 for complete repair kit including the extra oil stop cables. well worth it if you have only just got oil at the camshaft solenoids (magnets). otherwise as with me a new engine wiring loom. £376.00 from Mercedes, Cheapest.
I intend to do a step by step "how to" because replacing the wiring harness at first seems a piece of cake, until you come to the cable going underneath to the lambda sensors etc. I did it the hard way and I spent 2 days before realising there is an easy way. This involves removing the supercharger which you have to remove in both cases. I have made a boob up and put it all back and now realised the crankshaft sensor plug is not connecting (must be loose) so another couple of hours. hope this brief outline helps. Does save a small fortune.

 

[tesla6518]

another quick point the camshaft solenoids (magnets) have small rubber plugs that are fitted after alignment. the best way is to immerse them in boiling water.then place a 3mm drill bit (the part that fits in drill) in the hole in the plug, while pushing in the plug use a flat blat screwdriver to go around the plug giving it a good push. warnings; do not push too hard on 3mm drill easy to go through rubber, when you think the plug is in check gently with a screw driver and put something underneath as they come out and get lost quite easily even when you think they are in

 

[tesla6518]

An update to my oil in the wiring loom. Well it seems the garage who used to do my MOT,s each year kept telling me MOT failure due to O2 sensor ( they had a Merc specialist) however it seems the engine was pushing out rubbish into the Cat (no fault codes) and blocked it. Mercedes price £800 but no delivery date. Tried all over Europe to no avail. Sent to a cat company who said they could clean it. When they got it they said the holes were too small so they couldn't clean it, but to their credit they gave me the name of someone who could help. Am I going to reveal the name. Well.
Of course I am it is Catman based in Southampton (any problems contacting send me an email) within minutes he told me he could get the front end pipe with Cats at a price of £370 delivered next day. Well it turned up the next day as promised complete with a new seal.
I would recommend getting some 8mm x 45mm 8.8 high tensile flanged bolts. This is because the flanges are slightly thinner than original.
So all fitted and back for MOT. Oh Yes!!! Failed again. High CO.
After a lot of soul searching, research and talking Mercedes technicians, it seems that the engine management computer gets clogged up and even doing a full adaptation.it is not reset.
Therefore a software update has to be performed. This is being done Wednesday . I will update you then. Oh yes the cost is £50 from an indy.

 

[alexanderfoti]

Yes, this is quite common and the adaptions get stuck. I would have said high Co cannot be cats, only high Hc