I need some emmisions help :-( the volvo failed.

HC 1.0929 ... limit is .8

CO 8.77 .... limit is 15

Nox 4.95 ..... limit is 2.00

What might this be? Needs to get passed for registration.

That CO is real high, and that means its running rich. Fix that and the others will fall into line probably.

CO is within the limit and NOx is high, so how could it be running rich and causing those readings?

I am assuming that the 15 for CO is a misprint. It has to be 1.5. Thing wouldn't even run at 15% CO. Modern engines got an allowable CO of like .005 % or so. Even in the early seventies fuelie engines were held at 2%. So it must be rich.

I agree that vacuum leaks need to be checked for. NOx and mildly high HC indicate that much. Also inspect your O2 sensor - check the voltage (once hot) as you rev the engine - is it responsive to changes in throttle, or sluggish and lifeless? Is the voltage in the stoich range? If not, you might need to clean or replace it.
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Speed Racer, '83 240 R, '74 164 E, '93 940 OL1 (Manchester, CT)

High Nox is typically symptomatic of a lean mixture, which drives combustion temperatures up, favoring formation of oxides of nitrogen. Although your CO looks normal, I would do a thorough search for vacuum leaks... intake snorkel, manifold gasket, injector seals. I see your HC is over the limit, too... so check your O2 sensor (read the 700/900 FAQ's) and also your fuel pressure regulator. And of course, don't neglect the basics - fresh plugs, cap + rotor, air filter, fuel filter, flame trap. A can of dry gas or Techron in the tank and a good hot run (might be tough in Wisconsin in the winter!) just before the test is a good idea, too.

You didn't mention what year or how many miles on your 'bad' Brick. There's a possibility that your cat is shot, and lastly I'll mention that if everything simple is OK, then on '88 or older models you can retard the spark to get the Nox down.


Good luck, and let us know how you fare.

What year is the Volvo? Guessing you don't have a check engine light on. Did you check for any error codes? Being mostly a NOX problem first thing to check for is vacuum leaks.