Hey everyone, I am seeking advice on what the problem is to get my Civic to pass smog. I am trying to do this legitimately but it seems I may have to go the illegal route, but before doing that I am inquiring for some assistance.

First off, let me tell you what the problem is. My Civic is failing CA smog because of high NOx (low speed only). It has been in the shop for a while, which is owned by a very reputable smog technician. So far he has managed to bring the NOx down to about 1200ppm from 2700ppm, but for some reason cannot get it to pass (max is about 730ppm). The work that has been done is: New header o2 sensor, New Napa catalytic convertor, Decarbonized the engine, Fuel system cleaned, and retarded the timing back all the way he could.

Now let me tell you what car it is, it is a 1995 Civic VX hatchback with the D16 swap. Everything is stock except the intake (c.a.r.b. legal). From what I was told, the motor has about 90k on it. Another thing, the check engine light comes on intermittently. I am starting to think it may be an evap leak, but I am not sure. I have not been able to locate the jumper to pull the check engine light codes, it appears to be missing.

Any help is greatly appreciated!!

 

The correct thing to do is first pull the code(s), see what is causing it (them) and go from there.

If you don't want to / can't do that, and your engine has an EGR, clean it out and verify that it is operational.

But, if you just want a little help passing right now:

Lowers combustion temps, which reduces NOx production.

 

The mechanic that worked on my car informed me that the D16 for my year does not have an EGR.

I have also been told that there is a chance my car does not have a California ECU. Could this be true? I have checked the numbers and the ECU does match with the motor, but I have yet to find anything about whether or not it is a California ECU.

 

The Civic VX has a D15Z1 engine. What engine do you have?

 

My car has the D16Z6 swap.

 

Didn't even notice that before.

If you have a swap, have you taken it in for the BAR sticker for the swap? The different engines could very well have different smog restrictions. It might be passing what is allowed for the D16, but not what is allowed for the D15Z1...

 

Obviously the engine has been swapped. Check what ECU you have.

 

Ran the numbers on the ECU, they match up with everything perfectly.

Since the car has had the timing retarded back, new o2 and decarbed, I have noticed significant power loss. Car doesn't really pick up until the vtec kicks in. This did not happen until after I got it back. Although it is almost passing, something else is causing it to fail.

I'm thinking of trying the Iso Heet method...

 

Did you check the plugs gap? Timing?

 

the vx motor was a fuel efficent motor not to mention its a 1.5 compared to a 1.6 granted size isnt much bigger but there could be a higher NOx number allowed for the d16 somthing u should look into


ps love illinois haha no smog test dont even need to take it in if older then 96 haha

 

Amen brotha . Car is registered to my dad in Illinois since it kept failing inspection in Jersey. Cops don`t like me so they follow haha.

 

NOx should actually be lower for a Z6. The cali spec VXs didn't have leanburn because they wouldn't pass CA emissions when they were new due to the high NOx numbers.

 

From CEL sticky at the top:

Do you have a P28 ECU?

 

Yeah, here are the numbers that are on my ECU.

37820-P28-A02
760-802353

 

Okay, Here are the pictures of my ECU and the surrounding area. Please note that I bought my car this way and I am in the process of cleaning everything up and properly mounting the ECU to the car. There are no visible jumper wires for the OBD CEL.

 

see that green tubing in the passenger's side corner of the dash? Pull those wires down, the two wire plug on the end is the plug you'll need to jump to read the codes.

 

Okay, I pulled the codes today. I got 1, 41, and 22.

1 = O2A - Oxygen sensor #1
22 = VTEC pressure valve
41 = Primary oxygen sensor heater

 

If you reset the ECU, do all codes repeat?

Fix O2 sensor codes 1 and 41 and you should be good to go.

 

which o2 sensor is this code coming from?

 

There is only 1 oxygen sensor on that particular engine/car.

 

I just replaced my oxygen sensor about 2 months ago (brand new), could it be defective?

 

Could be, or someone didn't do the VX O2 sensor trick properly (if it's a federal VX, CA version came with a 4 wire O2 sensor, except for '92)

If you used a Bosch O2 sensor that may be yout problem.

 

Keep in mind, it's a VX with the D16 swap. Does what you say pertain to the D16 as well?

 

O2 sensor codes do not necessarily mean the O2 sensor is bad. Check the wires with a multimeter.

 

Here are the codes I pulled this time:
1 O2A - Oxygen sensor #1
10 IAT - intake air temperature sensor
21 VTEC spool solenoid valve
41 Primary oxygen sensor heater