Hi Scotty, I have a 1996 Dodge Dakota 3.9L 2WD Auto with about 118,000 Miles and her in CA it failed smog so bad some years ago its now a "Gross Polluter" and has to be smogged every year. Back when it failed in 2011 it was on its original Catalytic Converter but the replacement got it to pass by a fair margin.
It has no OBDII codes, occasionally stalls when first started, rarely will struggle to start or rough idle until warm, has low power after about 3000 RPM, and will sputter initially after a couple ignition cycles in the same day but runs okay otherwise
Last year the Cat went again
I have High NOx after
- New Catalytic Converter specific for the model
- New upstream O2 Sensor
- Spark Plugs, Wires, Cap and Rotor
- New rubber connections on Vac Lines, replacement Brake booster and Master Cylinder since the old one was leaking.
- New Temp sender and Thermostat
It still has High NOx and this year was not equipped with EGR
the only thing I can think left is a Plenum Gasket and hoped you may have some input.
It's sentimental so anything helps