Civic VX Failed Smog Twice
 

So I'm getting frustrated with my civic vx which is my backup car and car that I used for pizza delivery for 8 months while in college. Now that I want to sell it I can't pass smog, even though the last time it was smogged which was 1.5 years ago, it passed with flying colors. Now I'm getting ridiculous amounts of NOX that is driving me insane. I've done many repairs but can't seem to pinpoint what is causing me to fail. Below is a list of everything I've done.

Retarded Timing to 13 Degrees (125,500 Miles)
Recleaned EGR and EACV (125,000 Miles)
New Distributor Cap and Rotor (125,000 Miles)
New Thermostat (125,000 Miles)
Replaced Input Shaft Bearing and Axle Seals (125,000 Miles)
New Radiator (122,000 Miles)
New Clutch (118,000) Miles
Replaced Throwout Bearing (118,000 miles)
4 Wire 02 Sensor (Auto Parts Direct To You)
NGK Spark Plugs (NGK Website)
Fuel Filter (Honda OEM)
NGK Plug Wires (NGK Website)
Exhaust Manifold (Dorman 674-545)
Cat Converter (Dorman 674-545)
OEM Honda Timing Belt Change at 115,900 miles
Water Pump Replaced at 115,900 miles
Replaced Stock Muffler at 115,800 miles
Cleaned EGR Valve at 116,100 miles
Cleaned EGR Ports/Intake Manifold at 116,100 miles
Cleaned EACV at 116,100 miles

While I had my pizza delivery job I had converted the car to Fed with the new ECU, conversion harness, and 5 Wire O2 sensor. After it failed with the Fed conversion I decided to go back to CA ECU and new 4 wire O2 sensor. My results with the CA ECU and O2 turned out worse than the Fed. I have no idea what is wrong. I ran Guaranteed to Pass and Gumout Fuel Injector Cleaner already. I even ran it close to E before my last test and filled it with 1.5 quarts of Denatured Alcohol and still it did not pass. (And yes I've now diluted the alcohol with regular gas.)

The only current problem with the car is that it has an intermittent CEL with code 1 for oxygen sensor or sometimes code 0 for ECU, they are never both on at the same time. I tried switching over to my FED ECU to see if I get a CEL and I get code 41 for primary o2 sensor heater. I don't see why anything would be wrong since I've tried the old and new o2 sensor and still get the same codes. Also, I have an extremely low idle with the car, it will idle all warmed up at about 200 to 300 rpms, it has never died but I can't get it to idle higher without experiencing a fluctuating idle. Oh and the EGR was tested and works fine. Can anyone help out?

You gave us everything else, Might help if we know which year and motor this is.

What caused you to do all the work in the first place? http://forum.ecomodder.com/images/smilies/eek.gif
http://forum.ecomodder.com/images/smilies/eek.gif Did it pass before the work?

Anyway if its running a tad lean it won't pass emissions if you just want to pass you will need to get her to run a bit richer and the Nox at least will clear up.

Sorry, it is a 1994 Honda Civic VX (California Model) with the VTEC-E engine. I did the work because when I bought it, it obviously hadn't been really well maintained but it passed smog in its condition which I have the papers for from the previous owner. And so, as with any good owner, I gave the car a tuneup since it was only getting 32 mpg and thought with all my work it would run so much better and pass smog with no problems next time. Well, now the car runs great and I get 44 mpg and feels great, but I don't know what makes it run so lean.

I don't know why it's running lean, either, but what if you screw with the MAF by wiring a small resistor in parallel with its sensor circuit?

The other thing I noticed is: These things are built much more cheaply than the original ones.

I'd scrutinize the cat and the EGR, since both of those have been giving you problems and are there to reduce NOx.

You talk about having made the mods to convert it to Fed standards, but it didn't pass. With the Fed standard you had or should have had a 5 wire oxygen sensor.

Since you didn't get it working on the Fed standard, and you've chosen to try to go back to the Ca standard, I wonder if you undid the wiring changes you would have needed to make.

Given the fact that you were able to pass with the Ca setup a year and a half ago, I would be very surprised if the ecu is really guilty of causing you any problem.

One thing to keep in mind, the voltage outputs and control of a 4 wire vs a 5 wire oxygen sensor do not operate the same way. You can not swap a CA ecu and a Fed ecu back and forth because they operate and are controlled differently.

Best of Luck to you.

Thank you Whoop's for making me think a bit when you mentioned, " I wonder if you undid the wiring changes you would have needed to make." Because of this I went back and looked at my ECU pin layout and found the appropriate ones online to compare and match the layouts. Ok, so I think I've found my problem and it lies in the ECU. I found two pins which were very similar in color and they were switched. This was for the primary o2 heater and LAF sensor. So I'm pretty sure things will be much better now. Also, I have some concerns regarding other pins, and if anyone can help me out I'd appreciate it. So I looked at the ECU pin diagram for the VX in both the downloadable manual (2nd to last page, pg. 1257) and also at an OBD1 pin diagram I found through google search. Both tell me what color the wire should be and the one I found online also tells me what it's used for. Here are my findings:

A11 is said to be Orange/Blue or Red but mine is Pink (EGR)
D3 has quite a bit of electrical tape (Knock Sensor)
D11 is said to be Light Green or Red/Black but mine is Pink (Throttle Position Sensor)
D17 is said to be White but mine is White/Pink (MAP Sensor)

I don't know if the color variations really matter at all but I'm just trying to get everything done and done right. Thanks!

Passed smog on monday of this week! It was just the switched wires, all other wires are fine. Nox levels were below 50! Now it's time to sell it!