High CO during emissions test

During the high speed run of my emissions test the CO levels were high, which apparently indicates rich air/fuel. I am planning to change the oil, air filter, spark plugs, and possibly the plug wires distributer cap and rotor. Any other suggestions or tips... The jeep runs great not sure what else it might be, O2 sensor?

boostedvdub80239 said:

Any other suggestions or tips... The jeep runs great not sure what else it might be, O2 sensor?

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An oxygen sensor's a possibility, but so are a few other things. What year is the Jeep? Engine, transmission, 2/4WD, etc?

1990 cherokee, 4.0l 4wd, 5 speed

i'd do O2 sensor if it hasn't been done. not only will it probably help your emissions but help your fuel economy. our 4.0's are considered low emission engines. they don't fail emissions often unless something is wrong.

o2 as well.
but i did that and still failed CO. turned out to be my cat.

replaced and was so clean it wasn't funny.