190e smog test problem

300E Catalytic Converter Test

1988 300TE fails emission test and valve job

Failed emmisions test!

My 93 190e 2.6 Failed the emission test, tech help

Lots of ideas in these threads. Many point to a worn out cat.

One simple trick that might help is to first drive the car on the open road a fair distance - get it good and hot, then take it straight in to the testing facility. Try to be the first one in line.
Fully warmed up engines supposedly run a little cleaner.