Hey so I cannot pass emissions on a 1994 Civic CX with the stock D15b8 engine and transmission.

So I have changed the Cap, Rotor, Wires, O2 Sensor, Coolant Temp Sensor, inspected the Exhaust (Found out the cat was gutted before I got it), new spark plugs (checked gap), Adjusted ignition timing, Adjusted Timing belt. Checked everything 3 times.

I really don't know what else to check. Any one else have this experience?

my test values
508 HC (Max 220)
13.1% CO2 (Max N/A)
0.86 CO (Max 1.2)

I was told that the car should be able to pass emissions in Tennessee without a Cat.

Aside from that the car smells like its running very rich. I just can't figure out why. I know I don't have a Cat but putting a cat in won't really help with the high HC very much. I think it's just running way too rich and I don't know why. I'm thinking the Fuel Pressure regulator may be the cause but I am out of ideas. Any help would be greatly appreciated!

 

One of the main purposes of a cat is to convert unburnt fuel (hydrocarbons) into CO2 and water so that alone is going to reduce your hydrocarbon levels and is probably a good reason why it "smells" like is running rich..... Unburnt fuel is coming out the tail pipe.

If it is running rich though a few things you can check or is a stuck or leaky injector, clogged air filter, bad MAP sensor, bad ignition coil. Those are a few good places to start.

 

X2 above post. Put a high-flow cat back in it(then you'll pass) they're about 120ish After install. You'll get mileage And a tiny bit of power back that you are losing from running rich.

 

A cat will most definitely solve the HC issue. The money spent on the other parts could've solved the issue at hand.

 

get a cat

 

Ok. I'm working on getting a Cat. If anyone has one they want to sell me, please chime in. Its the type that bolts straight on to the manifold.

What I don't understand is why are people are saying it can pass without one?

 

It will exceed the hc lmit for your car w/o it no matter how much you lean it out. Like goldsy said the primary purpose of the cat is to reduce hc.

 

Because is serves a function required to pass emissions.

 

Yeah I understand what you mean or cars wouldn't have them in the first place. What puzzles me is that people tell me that they were able to pass emissions in TN without a Catalytic Converter. Either way I'm going to put one on, not trying to get around that. The car stinks and I want to fix that.

 

Those people are making up ****, or they are passing obd2 emissions, I can pass in my EVO and STI without cats, put them on a sniffer though and they would fail.

 

It's running very rich. I don't think the lack of a cat alone could explain all those hydrocarbons.

Any CEL codes thrown? Is there an exhaust leak in the header near or upstream of the O2 sensor?

 

thanks for clearing that up.

 

Not one! That's what's so frustrating. I'm beginning to think the ECU may be going bad. When I unplug the O2 sensor from it just to see if it will throw a code, it doesn't! There was a code stored for the ECT sensor so I changed it and the temperature is reading slightly higher now, not as low as before. There's no exhaust leaks I can find. The O2 sensor is sitting right outside the exhaust ports so even with a small leak its unlikely that it would cause a huge problem.

I'm wondering if the injectors got changed to larger ones. I heard somewhere that the CX and VX Civics used slightly smaller injectors (~180-190cc) and the DX, Si models (~240cc). So maybe the injectors when before and a previous owner changed it to the wrong ones. Or like I said, Fuel Pressure is too high. I'm going to check the vacuum and fuel pressure with a gauge when I get a chance to rule that out.

Plus, running rich could destroy a Catalytic Converter fairly quickly as well.

 

A bad ECT sensor or circuit would definitely make the engine run rich. Which ECT sensor did you replace? Your engine has three. The ECT sensor related to code 6 has nothing to do with the temp gauge in the cluster.

Is code 6 still thrown?

Even a small exhaust leak in the header could make the engine run very rich.

It's worth figuring out what injectors are installed.

Checking the fuel pressure is also a good idea.

No question about it.

 

So Code 6 is gone now. I changed the one that bolts into the head under the distributor. I didn't know there were 3 though. Only other one I know about is the one that goes to the fan switch to make the fans go on.

I am going to check for exhaust leaks again as well as fuel pressure and vacuum. And double check those injectors.

 

There are two ECT sensors that plug into the block under the distributor:

• The 2-wire sensor is what would throw code 6.
• The 1-wire sensor is for the temp gauge in the cluster.

There is one ECT sensor that plugs into the thermostat housing. It has 2 wires and controls the radiator fan.

A vacuum leak won't make the engine run rich.

 

Ok well maybe the temperature thing was just in my head.

 

You can test the unplugged 2-wire ECT sensor under the distributor by measuring its resistance when the engine is fully warmed up. It should read 200-400 Ohms.

 

Yeah I did that, I put it in some hot water ~180F and measured it, Came out to about 460 so I just figured I would replace it. It wasn't too expensive. Map sensors are a lil more though. And TPS sensors are probably not causing it. The O2 sensor was jumping all over the place from 0-1V and after I changed it, the values seemed to have a more predictable change. Car seems to run a bit smoother. I also ran some sea foam through it to see if that would help.

I'm going to check on those injectors, vacuum leaks, and Fuel pressure when I get a chance.

 

Again, this^ test is irrelevant to your emissions problems. If you had a vacuum leak, then you'd have a high or hunting idle, not an emissions problem. That being said, there's also no harm in doing the test, just no value in this case.

 

That's what I thought too, but I'm fresh out of ideas...

The car runs good, idles smooth and quiet, has decent pick up as far as what you'll get from a 70hp engine.

 

Google how to cheat emissions, super street did a great write up a few years back there are a couple tricks you can do but you have to have a cat

 

get a crooked smog and hope you dont run into any highway patrols ha

 

Some one told me an 1/8 of a tank of gas + 99% isopropyl alcohol would do the trick. He said its pretty much fool-proof. But there is a crooked smog guy out here I heard about. I'm just not sure how reliable that info is. These places are not like California where they are privately run. The emissions places are run by the state.

 

Just fix the problem the right way so the engine runs properly. Then enjoy the long term benefits, such as good gas mileage and the cat no dying soon after installation.