failed smog

[dawkid]

93 ranger v6, truck passes everything but the NO,s, i replaced the cat, and done a tune-up on it, i wander if replacing the O2 sensors would help, they never been replaced, no "engine check" light on but i know there must be a reason for the failed test, help!
yhank you.

 

[MAKG]

High NOx means high cylinder temperatures.

Vacuum leak, poor grounding, inop EGR (if equipped), etc.

And if you're going to guess, go to a shop. It will cost less and be FAR faster than replacing oxygen sensors that aren't likely to be a problem. And you replaced a cat FIRST? That's how you spot an incompetent exhaust tech.

Cats plug or get damaged, but they do not wear out in a few hundred thousand miles.

I have a factory original three-way cat on my Prizm, with 280K miles on it (as well as two original oxygen sensors), and it sniffs just fine.

 

[almostclueless]

MAKG is spot on.....getting a decent dealership shop to diagnose it will probably end up WAY cheaper thanm throwing parts at it.

 

[kamps989]

move to Minnesota where you can do whatever you want as long as it doesn't rattle to many windows!!!