C220 Petrol Emissions

[alssnape]

Hi, My dads 1997 C220 Petrol has just failed the M.O.T on emissions.
The CO reading is 0.6 (double what it should be) Lambda is giving a good reading of 1.02.
I have checked the throttle flap and the air flow meter but both seem ok.
I have also given the car a good blast up the motorway as my dad only does short journeys at low speeds.
It had a new cat fitted last year so I don't think its that.
Has anyone had this problem, or could someone point me in the right direction.
Thanks for reading this
Adam

 

[recycledjuvenile]

make sure the temp is close to 100 degrees when you retest it. it may jsust pass.
you could try changing the maf. it may be on its way out

 

[television]

make sure the temp is close to 100 degrees when you retest it. it may jsust pass.
you could try changing the maf. it may be on its way out

At times in Sweden it was a problem getting the level down, and we would drive the car locked in third for a few miles and get the engine up to 100c. As you say the MAF could well be on the way out

 

[alssnape]

Thanks for that guys.
The temp could not be any hotter than I got it for the test so I will have a crack at the MAF.
Cheers
Adam

 

[bigasotonuk]

Hi,
Was the CAT a genuine Mercedes item? As some of the pattern ones are fitted further back in the system than the Mercedes item and will take a long time to get up to temperature.

 

[bouncer]

Was the lambda sensor changed at the same time as the cat last year?
The CO level is twice the generous limit, this does point an emissions issue before the cat. It could be the lambda sensor. The lambda reding on the emissions cert does not tell you the condition of the sensor. (Lambda is greek for ratio)
Do you have the rest of the emissions results, may be able to help if i can see the rest.

sTeVe