For the 4th year running my 190 hasn't passed smog check. I am now at my wits end trying to solve this and need your help.

I don't have the numbers in front of me right now but on the result chart, It passed at 15 mph, but not a 25mph. The only value not in spec was the Carbon monoxide reading and it was over double what passing is.

Where should I start looking to solve this problem.

Thanks

Gregory

__________________
Current
2006 E320 CDI, 57K bought at 67K "Liesl"
1986 190E 2.3-16, 198K bought at 56K "Brigitta"
1987 300TD (Chuggin Along), 292K "Friedrich"
1995 E320 Wagon, 200K "Louisa"

Past
1987 300SDL, (sold) 125K, bought for 1$ "Kurt"