Uh OH - EMISSIONS FAIL - Oxides of NITROGEN (NOX) - HELP?

[castlerox]

I went to emissions today.

Everything is cool but...

See images below. Anyone know what the problem may be? I am not that mechanically inclined...

Thanks for your info if you have some!

Matt
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1985 Wolfsburg weekender SVX
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[AtlasShrugged]

High NOX happens when the combustion chamber temperatures are high. There are a couple of tricks to get it down for emissions testing.

1. Do not warm the engine up prior to testing. The coolant temps should just be coming off the cold area on your gauge. Keep the cylinder heads cool. This will increase your HC, not a problem if your Catalytic converter is working and has "fired up" and your O2 sensor is working. You will still pass the HC and your NOX will be lower.

2. En-rich the fuel mixture..this works sometimes..if your O2 sensor is not working.

3. Replace the catalytic converter (when your emissions numbers are so close to passing..it could be your Cat is not working). When the Cat gets to the end of days it will not scrub the NOX. BusDepot and RockAuto have them for about $100 to $120

[Howesight]

Your HC and CO are so close to the limit that this is obviously a cat converter problem. With a new cat, functioning oxy sensor and no other problems, you would be well under the test fail limits.

If your oxy sensor was bad or almost dead, you would most likely fail on HC. This is why I would suspect the cat and not other components like the oxy sensor. The default ECU mixture when the Oxy sensor goes bad is too rich to pass HC. Sub in a new "test" cat for emissions testing and after passing, use it next year again. Unless you wish to have emissions perfection in which case, use the new cat until it also fails.

If you don't have money right now for the cat, then retard your ignition timing 5 degrees just for the test. That may just do the trick. WBX engines don't have EGR. On engines that do have EGR, the low-load low-rpm spark timing can be advanced quite a bit to give good torque and fuel economy, but this only works if the EGR system is working. The EGR system cools the in-cylinder temps by introducing inert gas which lowers combustion temps. So, on the WBX, since it has no EGR system, a marginal NOx test failure can sometimes be overcome with a bit less spark advance.
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'86 Syncro Westy SVX

[desertrefugee]

+1 on backing off on the timing.

My Westy marginally failed the same test in Phoenix. I retarded the timing a few degrees and passed by a wide margin.

Give it a shot - and as already mentioned, don't have the engine too hot, contrary to optimizing for other emissions tests...

Good luck!
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[r39o]

The idea of getting it hot before the test is to make sure the cat works well.

If hot and all you do is fail NOX by a little, a new cat has always passed for me.
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[K58]

^^^^^^^^^^
this
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[desertrefugee]

[BillM]

[K58]

I ended up spending ~$700 to pass smog on my '84 this year. On the advice of my world renowned mechanic I bought a new CA Cat and it did the trick.
2 years prior he tweaked my timing for nothing because it was borderline.
Bottom line is, do what you have to do.
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Westy HID Projector Retrofit

[Umusername]

I am right on the edge as well and am trying to figure out the cheapest way to pass. Here are my readings.

I put a new air filter in and changed the oil along with some general making sure hoses are clamped on well.

[Howesight]

Hi Umusername:

You can pass by adjusting your spark timing. Retard it 5 degrees and you will pass. Then re-adjust to spec after the test. Your CO and HC numbers indicate that your cat is healthy.
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'86 Syncro Westy SVX

[photogdave]

I also just failed the NOx test. Vehicle reading 1410, max allowable is 1145. Other tests were fine: HC 53 (143); CO .48 (.71).
I have a brand new cat that came with the RMW SS exhaust. New 02 sensor two years ago.
The van was running fine (and passing AirCare) with the old leaking exhaust. The leak got really bad and the whole thing was rusty so I had it replaced. With the new exhaust there was a rough cold start idle. I replaced the temp II sensor (no change) and adjusted the screw on the AFM to bring the idle up a bit. When warm it idles at just about 1000.
What should I be looking at?
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[AtlasShrugged]

If you are your wits end and have nothing to lose..unplug one fuel injector just prior to and after arriving at the test center..if the engine is healthy it will barely idle..and will pass just fine. Your disconnected cylinder becomes an air pump and really cleans up the exhaust.

After the test..replug and go.

[Jake de Villiers]

[AtlasShrugged]

[tencentlife]

[bluebus86]

Well HC got a lot better by changing the air filter and tightening some things.

you could run the test with a cool engine now, the cool enginewill reduce NOx but increase HC, but since your second HC reading is s much lower now, you might be able to retest with a cold motor and pass both HC and NOx.

My van did simular and that is how I was able to pass once, the catalyst was really on the way out and next time two years later i replaced it and passed hot.

so you might if you have lowHC be able to get away with a cold test and be able to pass NOx. if not maybe time for a new catalyst. I am not a big fan of tweeking the motor wrongly to pass, unless you put it back right away. you dont want to be runing with reduced timing or really rich mixtures other than to pass a test. you dont want ot screw a whole bunch of things up just to pass a test.

if yoru concerend that you van is starting to eat catalysts (ie worn motor burns oil or such) you could place the new catalyst on only for the test, then remove it to save for the next test.

[Jake de Villiers]

Hey Dave, after re-reading your post, I'm thinking that you should put the AFM screw back where it was prior to your tweaking it. Its best to use that screw in conjunction with a tailpipe sniffer to set the CO at idle.

A lean miss at idle seems to be par for the course with Digifant-equipped WBX engines, anyway.
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[AtlasShrugged]

Yes the O2 sensor will kick the mixture lean..and if the engine will idle..they do pass the dyno emissions tests here in Metro Atlanta. I never had to disconnect to O2 sensor..you could..the clean air techs never have looked under the engine cover, only under the engine to be sure it has a Cat.

Try it if you have a buddy that can run a sample test for you..

..it should work just fine.

It would be a solution of last resort..don't drive around with the engine like that.

[tencentlife]