Civic89DX-Emission Test Failure.

Folks: Per Ontario / Canada standards for emission testing, my 89 Honda Civic DX1.5 failed on High HC, CO, and NO, on driving test, but the same for curb testing passed.

so I went and installed a new Cat Convertor, and went for the test the same day. It failed again on higher (than before) readings on HC and CO, while it passed on NO and the curb testing (with better readings).

Anyone knows why the HC and CO readings would go through the roof, and much higher readings than the test before, by installing a new CAT????

Anyone knows, besides the O2 sensor, what I can do to remedy the HC and CO readings, so my baby passes this stupid requirement???????

check for vacuum leaks and check/change the O2 sensor.

You might also check the TPS to make sure that it's giving the right signal for each throttle position.

hmm, do you have a header intalled? if so you might have to relocate ur o2 sensor, i had to do that with my si crx... cuz it was coming up with the same results.

Thanks guys.
I wish I had read your note about the header, earlier (I just read it, and for some reason, the email notification part did not work).

I went on the weekend to get diagnostics done and they toled me that because of the after market header I installed, the O2 sensor is located in the 4th cylinder pipe , rather than, by design, it being in the collector where all 4 pipes merge.

So they installed a brand new O2 sensor (in the same location) as they said that the sensor had gone bad. Not sure if they conned me into paying them for a new one, or they used the same old one, cuz it still failed test for HC and CO (the results were much better and CO reading was very close to the required), but I got a conditional pass so I could renew my plate sticker for another 2 years (which is what I was really interested in).

So I was out after $320, including re-test, cleaning, and new O2 sensor and labor.

The original part that I replaced with the header, has been lying in my backyard for almost a year, and suspect it is all rusted and not sure if I can re-use it, as the header has not done me any good. The mechanic said if the original part was there, instead of the after market header, my car would have passed the test.

In any case, if I continue using the header, where do you think it should be re-located, that that the crap from all 4 cylinders are monitored by the sensor i.e. near the collector. DIY instructions possible, for relocating the sensor??

THANKS again.

Go to ebay, or summit, or a machine shop.

Buy a bung that fits your O2 sensor... or whatever O2 sensor you wanna use.


This is the tricky part... Do you have a 4-2-1 or a 4-1 header? If you have the first one, you can get a sandwich plate made that will go between the upper and lower sections, but
1.) it will drop your lower section 1" and
2.) it will balance exhaust flow before it's supposed to.. you will lose torque.\

If you have the latter, just have it welded in wherever the "-1" part is on the header.

DC sports headers always came with a second bung down by the cat... you can also put it there, if you have a 4-2-1 style, and just put the plug from that one into your old hole... you won't even need to buy a bung if that's what you have.

If you don't have a DC header, you can always go back to "buy the bung, weld it on"

PS. if the mechanic told you "it would have passed if you didn't have the header" he's full of shit.

Mechanics will tell you that in spite... they think it makes them sound smarter. I've had mechanics tell me my car is "unsafe to drive, and should be junked" over a $44 part. (I hotwire my car to start it, b/c the main relay is bad, and I won't replace it.) They do it just in spite... I should know. I'm a mechanic :D

Honestly, if there was that much of an issue w/ the header, they'd have failed you at the visual inspection.

Thanks.
Mine is a 4-2-1 header type. I am OK for now, but before the next emission test, I will have to amend the O2 sensor. IS there a DIY available on this?

Thanks again.

Here's your DIY:

Sand a nice clean spot on your header's downpipe, right in front of the flange that bolts to the cat.

Get a nut that fits the threads on the O2 sensor.

Drill a hole in your downpipe.

Weld on the new nut.

screw in the new O2 sensor.

extend the one O2 sensor wire so you can connect it.

Find a way to make the old O2 sensor location appear to be still connected.
(only b/c "they" don't tend to like it when you move stuff around.)