1992 BMW 325is Failed the Smog Test for High NO, CO and HC

You will need to start off with a diagnosis. Usually a smog check repair station will charge around $50 an hour for smog failure diagnosis, and will require 2 hours to find out why your BMW 325is is failing the smog check.

We do not recommend throwing money at components which might not need replacement as BMW parts are not cheap. A smog check repair station will first conduct a quick look over for defective, damaged and/or disconnected components and will then move on to inspecting individual smog check parts, more than likely beginning with the oxygen sensor.

If your BMW need a single component replaced in order to bring emissions down and pass the smog check, you can be safe to assume in total you will spend $500.00. If your BMW has problems in more than one emission system, the repair cost will more than likely go higher. The point is to start with an accurate diagnosis.

Your BMW is a non-EGR valve equipped vehicle. Once all other emissions components are inspected, and either fixed or found to be functioning properly, we may suspect a damaged CAT (Catalytic Converter)… possibly plugged up. Vehicles which are non-EGR equipped rely heavily on the CAT for NO reduction. However you mention having replaced the CAT 2 years ago. We'd like to point out that the last time you replaced your BMW's catalytic converter may have simply masked your BMW 325is's emissions fault, and allowed it to pass the smog test. You may want to find out what the underlying fault(s) are so that if you end up installing a new CAT again you do not damage it.