Emission problems

[fredrik_bor]

I have an e-class e200 w211 m271 kompressor engine.

I cant get past inspection because of co being to high 3,6% and lamdba value to low 0,9
Obd scan says that the lambda before the cat is not working but ive tried to change it, then i tried changig thermostat, catalytic converter and air filter but
the emission test is exactly the same. Any tips? I have no idea what it can be, any tips?

 

[mattkh]

I cant get past inspection because of co being to high 3,6%

Mileage.???
When were the plugs last changed..?

 

[fredrik_bor]

Mileage.???
When were the plugs last changed..?

I have no idea, just read that this problem was a nightmare to fix. And i dont want to spend to much, but i can try change the plugs first too.

 

[malcolm E53 AMG]

Likewise when was the engine oil changed clean engine oil reduces the noxious vapours entering the PCV valve and it’s a good idea to change that as well it may have failed

You can buy an emissions additive to add to the petrol which should help and make sure the engine is nice and hot before the test is done

If all else fails you’ll need to check the injectors aren’t over-fuelling