Hey I failed my smog test today on my 93 civic with stock D15B7 can you guys give me a idea on what it could be. Thanks

I failed HC at 15mph (max)97 (meas)100

I failed NO at 15mph (max)731 (meas)1431 and at 25mph (max)798 (meas)1041

 

check air filter, spark plugs, dist condition, and ignition timng. how old is the cat?

 

Yeah I did a tune up a month ago.The car has 110,000

 

anyone

 

Looks like the cat wasnt warm enough or the cat is going bad from age.

 

So could it be the cat or the o2 sensor.

 

After you get the new O2 sensor, new cat, and warm up the car properly, you should see if you can advance the ignition timing.