Couldn't pass CO emissions test 2.0 TFSI / Help plz.

[MrGunch_]

Hi,

I cant pass CO emissions test for my mk5 golf gti. EA113
The idle CO readings are ok (0.090), but on increased rpm CO emissions are over the limit (1.150)
Before the last test, I changed sparkplugs, fully fixed leaking exhaust and changed Lambda sensor and cleaned MAF sensor.
Any ideas what to do or check next?

If I understand correctly, then in high rpms the fuel mixture is too rich?

Please give any advice or opinion.

[Carpy25]

The readings sometimes get raised by crank case gasses getting re-burnt get some fresh oil in there as any fuel contamination of the oil due to blow past  could show higher readings , especially if your normal driving means the car rarely gets up to temp to get rid of the gasses that build up in the crank case
If you haven’t had a recent oil change get that done before the retest
Also get the car hot before you roll into the testing station things expand when hot could help a bit

Rob

[MrGunch_]

The engine was runnning for more than hour before testing, last oil change 6 months ago, and if that would be the case i think then idling CO emissions wouldn't pass too, but the Idle CO test passed, but with increased rpms CO emissions, would skyrocket, like 6x the allowed. So i guess, engine is running too rich when increasing rpms? Plus Car last days, have started to have super rough idling when cold. Maybe any of the sensors are giving bad information to the ECU?

[LC5F]

Could be an air leak allowing unmetered air into the engine - lambda sensor detecting mix is too weak so tells ECU to dump fuel in to make up the difference.
My money would be on plastic PCV hoses that like to get crispy and crack.

[MrGunch_]

Ty for reply, thats next thing i will try, pcv + all pcv hoses and gasket.