fail emission helppppppp

[mrsatisfiher]

I have a buddy that has a 96 civic ls stock motor d16y7 fail the first time the nox level is kind of high and hc is kind of high when home change out both the o2 sensor now the nox is good but the hc is slightly high is that mean a bad cat? or anyone know what next to do

[HONDA GHANDI]

HC failures 9 times out of 10 are from bad ignition parts. NOX is usually a detonation problem associated with low octane fuel or too much alcohol in the system. Check the plugs, wires, cap and rotor. Put in some 87 or 91 octane and retest.

[mrsatisfiher]

thanks tobi