Reply To: Failed emissions test – think my cat is clogged but not sure

[emmataylor]

Catalytic converter cleaner additives get recommended a lot but the honest reality is that they work best as a preventive measure on mildly contaminated converters rather than as a fix for something that has built up deposits over fifteen years and is causing measurable backpressure and a failed emissions test. Spending money on additives at this stage is very likely to delay the inevitable replacement by a few weeks at most without actually resolving the underlying blockage. The mechanic’s backpressure diagnosis combined with your emissions failure and the sluggishness gives you enough consistent evidence that replacement is the right next step rather than trying cheaper interventions first.