my 1996 c220 wont pass smog its not the emissions? what can it be?

Doesn't sound that special. Find a local shop that supports this site. What were the codes? Start using Google to find answers on the boards.

Assuming the check engine light was on to begin with prior to the smog? And then additional codes popped up while the special place was trying to diagnose your car? Refer to your original failed smog report to address the original failures. If you can't find a Mercedes specialist in Stockton, there are plenty in Sacramento. We are a smog, diagnostic and Mercedes-Benz specialist.