I need help,I drive a 1996 Honda Civic DX No mods. I am tied against the wall. I don't smell emissions- like the cat is bad or something. No black smoke or anything. It looks and smells like it burns clean, although I do have a cracked exhaust manifold-would it cause it to fail this badly?

Fail-15mph: RPM-1786 ; %CO2-14.0 ; %O2-0.3|HC (PPM) Max-66 Meas-112 CO%-Max-0.57 Meas-1.20 ; NO(PPM)- Max-487 ; Meas-1620


Fail-25mph: RPM-1855; %CO2-14.4 ; %O2-0.2 | HC(PPM)-Max-49 Meas-84 ; CO%-Max-0.55 Meas 0.75 ; NO(PPM)-Max-774 Meas-1484


The car runs actually really good too.

Oh and the CEL isn't on.

 

It's probably that cracked manifold. That will let air into the exhaust stream, which fools the O2 sensor and causes the mixture to be wrong. Doesn't a cracked manifold fail the safety inspection there anyway? Where I live they don't check the tailpipe gas but a cracked manifold would fail.

Another thing that will make you blow CO and HC even though the car runs good and the CEL is not on is a bad thermostat. Unless the engine has warmed up fully, the computer will run it rich.

Or your cat is just plain dead, considering that the NOx is over too.

 

I think cars actually run better without all the smog gear. Cleaner is a different story.

I have a 1996 civic DX as well and it's a 49 state civic. Will be smoging mine in a couple months in California when I move there, but I think I'll get an exemption. However, just incase, I started running premium fuel (wish I could get ethanol free gas), put some injector cleaner in the tank, changed the plugs, caps rotor, wires, oxygen sensor and PCV valve. Cleaned the idle control valve, adjusted the idle and timing. 148k miles, was well past time to do all that anyway.

 

Do you think it's the exhaust manifold/cat and the cat underneath the car?

So I need a thermostat too?

 

I'm pretty sure the '97 DX (even California model) only has one converter, the one built into the manifold. The bulge in the pipe under the center of the car is merely a resonator, not a cat. So replacing the manifold / converter assembly should fix it.

Does your temperature gauge come up to about halfway and then stay at the same level while driving? If so, thermostat should be OK.

 

Yeah, it goes up a little under half. Yeah, it doesn't go up anymore than that.

 

"I am tied against the wall"
Back in the day CA used to have a program to assist people below a certain income level with fixing their emission troubles. Paid $400 for mine back in 2002. Might want to look into it and see if you can get hooked up. Otherwise, I'd recommend just taking it to a smog and repair shop if you can afford it. Unless you have the testing equipment yourself, this is pretty much going to be a cat and mouse chase beyond fixing the cracked manifold. Good luck.

"Will be smoging mine in a couple months in California when I move there, but I think I'll get an exemption."
Unless you're military, this is nearly impossible to do for post-1975 cars.