Hey guys just had my jeep tested and it failed... Only part it failed was the NO section, any ideas as what it could be? Fwiw it's a 94 4.0 just replaced the engine with a low mileage one.

probably running too lean, check your 02 sensor. I'd also check your air filter (that would make it rich though). Coach

Brand new air filter, it may need a new fuel filter but I don't think that would cause the NO level to be high...

I really like my smog guy! If one of my cars/trucks fails, he tells me what it needs. I go home and fix it, bring it back, and it passes.

:D

Yea I wish I personally would have went.... I sent my gf to do it while I was at school and the guy didn't tell her much at all.