high CO emissions from 1995 E420
 

Here in British Columbia, Canada, we are required to have an AirCare emissions test every two years in order to renew our car insurance. I just had mine done, and here are the results...note the results for the CO emissions:

hydrocarbons (HC)
average passing reading: 0.4469g/km
vehicle reading: 0.0549g/km
maximum allowable: 0.5

carbon monoxide (CO)
average passing reading: 2.4783g/km
vehicle reading: 6.4915g/km
maximum allowable: 9.32g/km

oxides of nitrogen (NOx)
average passing reading: 0.2755g/km
vehicle reading: 0.0897g/km
maxiumum allowable: 1.24g/km

This is what is written on the results sheet:

"Results more than 25% above the average, but still below the maximum allowable, indicate that a problem is developing or that key emission controls are degrading to the point where a failing result may occur in the future."

Where do you believe the high CO reading is resulting from? When I took the car in for testing, I had driven it hard on the highway for a two hour trip down to Bellingham in the summer heat...one hour each way...could this have contributed to the poor CO results, or do you guys believe something is actually more seriously wrong? Thank you for any insight...

On most MB's after 1992 with electronic Fuel injection, high CO is caused by slow response from the O2 sensor.

odd...I had the oxygen sensor replaced 2 or 3 times since I bought the car new...each time it was due to a check engine light...there are 48,500km on the car to date...I guess this is an item that wears/fails quickly...I'll have it checked out

Well, you did pass the emissions test ( complements of AirRip-off ).
If your fuel consumption is okay & you don't have a CE light, I would let it be.
Just because you're a little higher than " average", would not be of any great concern to me right now. ;)