95 C220 AZ emissions fail
 

Car has failed emissions 4 times now 2 times Nox was 2.01 standard is 2.00 latest results HC 0.69 CO 11.07 NOX 2.64 nox is all that fails everytime. Ive ran premium gas, used octane booster, is there
any adjustments like R16/1 or anything I can doto make it pass?

Thanks in advance for any help

I was struggling with borderline NOX on my 300TE here in AZ too...
Failed twice, got it third time...just about...

I plugged the EZL so there was no vacuum advance, then put 4 bottles of ISOheet and gave it a run on the freeway at high RPM's to make sure the cat was RED hot. I checked video cam's at the center to make sure I could drive right in.

NOx on the 1995 C220 is all about EGR valve operation. Make sure that the valve is getting vacuum from the switch-over valve.

Also with the engine running, if you supply vacuum to the EGR valve does the engine almost shut-off?