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Forum > Failed Smog Test > Question

What are my options to improve NO emissions for an 1986 Porsche 944 Turbo I've had for 20 years

This car has always easily passed smog tests, and this year both HC and CO are still fine, but apparently NO max levels have been lowered and my car failed this test. Since it appears from the HC and CO that combustion is complete and clean what can be done to improve NO emissions or to get a waiver.
Answer:

Typically a new Catalytic Convertor will do the trick. you don't need a factory CAT, there are many aftermarket and California legal CATs that will fit your Porsche 944. We only recommend that you ensure your 944 isn't running lean. The two things that will cause your Porsche to produce high NOx are the CAT and lean fuel condition. Lean fuel could be caused by faulty fuel injectors, defective fuel pump, and/or dirty fuel filter. posted by SmogTips Support

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