NOX emissions problem '90 Ranger

[Deekydoo]

I am needing some help and guidence at what might be causing my Ranger to have high levels of NOX which is keeping it from passing California emissions. The truck is in excellent condition for it's age, and I have always maintained it. I have only replaced the catalytic converter one time, and never have replaced the oxygen sensor. The oxygen sensor passed the emissions test so I am thinking of replacing the catalytic converter. It's been about 10 years and 60,000 miles so I'm sure it's due. I don't want to throw lots of money into it, and want to get it right the first time. My truck has over 208,000 miles and still runs great, just need to pass emissions. Please help if you have any suggestions. Thank you!

 

[RangerX]

Tell us which engine it has.
Here's a link to look at for starters: http://www.explorerforum.com/forums/showthread.php?t=219411&highlight=smog
and here's another: http://www.therangerstation.com/tech_library/CaliforniaEmissions.htm

I moved this to the Ranger forum.

Welcome to the forum.

 

[Sams01XplrSprt]

welcome aboard

 

[Tbars4]

...Here are a few reason's for failing NOx...

1. Defective EGR System
2. Faulty Catalytic Converter
3. Lean Fuel Mixture
4. Engine Overheating
5. High Engine Mileage