This was my first smog check with this car and I got stuck with a Test Only. I failed hard. I just want some internet diagnosis before I take the car back to get the once over and start repairs. Maybe I can do some of the work mysef to save time/money. Here's the numbers

HC CO(%) NO(PPM)
Test RPM MAX MEAS MAX MEAS MAX MEAS
15mph 1756 68 124 .41 .45 731 2707- Gross Polluter
25mph 1943 44 28 .41 .45 798 1147- FAIL

Car specs:
94 Civic DX hatch
Stock engine- No bolt ons just K&N
Exhaust system was replaced recently (before I bought) it looked fairly new.
I just changed the oil, seafoamed oil change prior.
Plugs, wires, PCV, dist cap/rotor, fuel filter are about a year old.
Ran "Guaranteed to pass" in the tank (followed directions). Looks like I get some money back from they A-holes.

Google says for a high NO reading its cat or EGR (94 civic = no EGR) But like I said, the catalytic converter/exhaust is fairly new looking (+/-5 years)

Any help?

 

My guess will be either O2 primary sensor is going out or the CAT is bad. Sometimes people buy cheap CATs just to pass smog. Even though you are not throwing a CEL, the O2 sensor is not switching fast enough to read the correct mixture coming out from the exhaust.

 

Check your ignition timing.

 

I have the same problem with my eg but I have a swap!!

 

Since I went to a Gold Shield shop, im going to have them do the repairs. From what the smog tech told me from looking at the numbers that: need to retard timing (am @ 18 degrees), replace O2 and possibly cat. It was a chain reaction. Advanced timing took out O2 sensor and that took out the cat (possibly).

So, if your having the same issues, I would look at those.

 

If that's their diagnosis, they're clueless.

Do you have your O2% and CO2% from the test? That way we can see your mixture strength.

 

CO2% - 14.9/15MPH 15.0/25MPH
O2% - 0.2/15MPH 0.0/25MPH

I just got it back, They bumped the timing down to 16 degrees, replaced the O2 and cat. She passed with flying colors.

 

K&N was probably part of your issue. These Hondas run a Speed Density system meaning the ECU has no way to measure the exact amount of airflow entering the engine, it can only guess based on throttle blade angle and MAP sensor readings. It will also cross check with the ECT and a few other sensors as well. Always go as stock as possible to the smog station in CA.

Also, how did they diagnose your cat and O2 sensor? If they just replaced it on a "hunch" you got ripped off more than likely.

 

i've got a similar issue. I pass with flying colors everywhere except HC (ppm) at 15mph. max is 68, i came in at 73. i've got new plugs, cap, rotor, air/oil/fuel filters. anybody know how to lower their HC level? Thanks

 

Replace O2 and run the car hot then run it into the smog shop.