Nissan Repair: 93 Sentra XE wont pass smog, carburetor system, power valve

Question
114k miles. Good compression. New plugs.

1st 15mph test:
HC = 28 max = 93
Co =.09 max =.57
NO = 1073 max 720

1st 25mph test:
HC = 18 max = 59
Co =.06 max =.55
NO = 1229 max 774

2nd test after new O2 sensor and new EGR valve
15mph test:
HC = 48 max = 93
Co =.14 max =.57
NO = 719 max 720

25mph test:
HC = 17 max = 59
Co =.05 max =.55
NO = 1032 max 774

3rd test after new catalytic converter
15mph test:
HC = 30 max = 93
Co =.02 max =.57
NO = 1327 max 720

25mph test:
HC = 20 max = 59
Co =.01 max =.55
NO = 1140 max 774

Do you have an idea what is wrong?

Thanks,
David

Answer
David,

I am getting old here.  But, if yours is a carburetor system it is the power valve.  If it is fuel injected you are going to need to check the injectors for being dirty.  You could get a set from a wrecking yard and do an ohms check to make sure you get good ones and that will save a few hundred bucks.  If not they run about $70 bucks at a parts store.