Kenji001

I have a 1993 S13 Hatchback with 240K miles.

The previous owner failed the smog check yesterday.

The result:

M1. 15MPH
HC: MAX 88 AVE 21 MEAS 28
CO(%): MAX 0.52 AVE 0.06 MEAS 0.08
NO(PPM): MAX 704 AVE 150 MEAS 775

M1. 25MPH
HC: MAX 53 AVE 13 MEAS 24
CO(%): MAX 0.50 AVE 0.05 MEAS 0.13
NO(PPM): MAX 738 AVE 136 MEAS 507

My friend help me to do the regular maintenance services after I brought the car.

We did:

Change engine oil and oil filter
Flush coolant and fill in 50/50 coolant
Clean fuel and change fuel filter
Replace air filter
fill up 91 Octane

I just smogged the car today and it failed.

M1. 15MPH
HC: MAX 88 AVE 21 MEAS 41
CO(%): MAX 0.52 AVE 0.06 MEAS 0.12
NO(PPM): MAX 704 AVE 150 MEAS 784

M1. 25MPH
HC: MAX 53 AVE 13 MEAS 31
CO(%): MAX 0.50 AVE 0.05 MEAS 0.10
NO(PPM): MAX 738 AVE 136 MEAS 432

How do I pass the NO(PPM) with 15mph? Any suggestion? Replace O2 sensor, catalytic converter?

Thanks!