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

[liamdaily]

Replaced the catalytic converter on my 2008 Altima after almost identical symptoms and the improvement in acceleration and fuel economy was immediately noticeable from the very first drive after the repair. Cleaner additives on a partially clogged cat at this stage are generally a waste of money because the blockage is typically physical deposits that a liquid additive cannot meaningfully dissolve.