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Forum > Failed Smog Test > Question

1988 BMW 325i - the emissions control systems visual inspections/functional check results passed

The ASM emmission test results passed at 25 mph, but at 15 mph only the CO % passed while the HC ppm and the NO ppm failed. What repairs should be performed by my mechanic? HC ppm meas 164 max 114 CO% meas .59 max .73 NO ppm meas 2099 max 785 This is the 1st time it's failed in about 8+years. Since the last smog test 2 years ago, it's only been driven about 3000 miles, mostly highway.
Answer:

Your BMW is a non-EGR equipped vehicle which means most of the emission reduction load is placed on the Catalytic Converter. The important thing here is this... if in fact the CAT is damaged, it is important to ensure a pre-existing problem is not the culprit. You don't want to damage the new CAT. A CAT melt down usually occurs due to high CO (Rich Fuel), old age, and extreme heat. It is recommend to suspect the CAT after a complete emissions system diagnosis. posted by SmogTips Support

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