MOT fail - Merc c200 kompressor 1.8 (W203)

[Antiloops]

Hi guys, could you give me some general advice on this please?
I had the car in twice with management light on and both times the garage said they couldn't pin point the exact issue, so I should carry on driving and see what develops... ( they said it was giving fault on the oxygen mixture but that was it)
Also had the downstream lambda sensor replaced by them last year.

Now they told me its either the upstream one or cat..

Thanks

[SonicShadow]

You can test the o2 sensor with a multimeter. If it's throwing an o2 related code then it's a good bet.

[Antiloops]

thank you Sonic

[CraigyMc]

Antiloops said:

Hi guys, could you give me some general advice on this please?
I had the car in twice with management light on and both times the garage said they couldn't pin point the exact issue, so I should carry on driving and see what develops... ( they said it was giving fault on the oxygen mixture but that was it)
Also had the downstream lambda sensor replaced by them last year.

Now they told me its either the upstream one or cat..

Thanks

Those carbon monoxide readings (11x the limit on the first idle test) suggest too much fuel for the air.
It's very likely that there's a sensor fault - O2, MAP, coolant temp, MAF.
There are other possibilities. Duff injectors, broken fuel return line, poor tuning map.

[Krikkit]

I'd hazard a guess at the engine-side lambda being knackered, but you'd need an oscilloscope to really see what's happening with it. You could throw a new one at it for £100 or so, but it's only guesswork without the diagnostics!

[Jazoli]

Have you checked the breather pipe under the airbox which is notorious for splitting on these causing all sorts of issues with the idle and emmisions?

[Antiloops]

Thanks guys,

What are your thoughts on using local garages instead of main dealers?
Main dealers are more expensive for sure but it seems to me that the issues start to happen when using local garage... Paranoia?!

[Krikkit]

Find a better one. Main dealers are (in my experience) parts-swappers at best, with hugely inflated labour rates to pay for glass palaces.

They have the best diag equipment, but often no-one who knows how to use it!

[dibblecorse]

Antiloops said:

Thanks guys,

What are your thoughts on using local garages instead of main dealers?
Main dealers are more expensive for sure but it seems to me that the issues start to happen when using local garage... Paranoia?!

Find a specialist, not as expensive as main dealer but better experience of the marque than a general garage, that would be my advice, maybe tell us where you are and people may be able to recommend someone / somewhere

[Antiloops]

Jazoli said:

Have you checked the breather pipe under the airbox which is notorious for splitting on these causing all sorts of issues with the idle and emmisions?

No I have not, I am a noob when it comes to mechanics...

[Antiloops]

dibblecorse said:

Find a specialist, not as expensive as main dealer but better experience of the marque than a general garage, that would be my advice, maybe tell us where you are and people may be able to recommend someone / somewhere

I am in Norfolk, Kings Lynn...

[Vaud]

Try calling

www merc-pro.co.uk

[Sheepshanks]

Antiloops said:

I am in Norfolk, Kings Lynn...

You're mid-way between Fleet Road Garage and MB Auto Centre. I had a look on the MB UK forums and they both get mentioned once or twice but nothing very conclusive.

Will Robinsons discount for older cars? The indies tend to use pukka MB parts anyway so the only saving is on the labour rate and if Robinsons will discount the convenience may swing it for you.

[Antiloops]

Thanks Guys, I have emailed MERC-PRO and I am in contact with them now.

[Gepkarcsi]

Hey
I got the same problem with my c180 kompressor 2003
Can you remember what was the solution for your problem?

Antiloops said:

Hi guys, could you give me some general advice on this please?
I had the car in twice with management light on and both times the garage said they couldn't pin point the exact issue, so I should carry on driving and see what develops... ( they said it was giving fault on the oxygen mixture but that was it)
Also had the downstream lambda sensor replaced by them last year.

Now they told me its either the upstream one or cat..

Thanks

[Disco_Biscuit]

Gepkarcsi said:

Common to get oil ingress in the engine wiring loom on that model causing O2 sensor faults.