Hi, I just recently failed smog. I pass at the 25 mile an hour part with flying colors. But at low rpm my nox is thru the roof. I replaced the cat, lower exhaust o2 sensor and it still fails. Aside from replacing upper exhaust o2 sensor, what else can I do????? Your help is greatly appreciated and much needed. Ty
Dec 8, 2009 at 2:08 AM