Emissions Question

I have an 88 240 wagon. 321K miles. Every two years in AZ I get the
emissions tested, and I fail. Alway NOX that fails. I get a new
catalytic converter, and it passes. Any suggestions as to how I can
make it pass two years from now?

Thanks!

John

 

That's odd, my mom's 245 had its catalytic converter crumble inside and
it has continued to pass the emissions inspection in WA with plenty of
room to spare.

I've heard of some blocking off the ignition advance vacuum line to
reduce NOX, you might try that.

 

Obviously the Engine is not working correctly, have you had it checked
against the specifications from Volvo (for CO, CO2, HCs, NO, O2 etc)?

Being within national vehicle test standards does not necessarily mean
the engine is working properly. You need to get to the bottom of the
problem. for example, if your cat keeps going you may have a problem
with overfueling, showing up as a high HC reading.

 

NOx emissions happen at elevated temperatures. Unlike most forms of
pollution, which decrease at higher temperatures, NOx actually increases.

I have an 82 240 wagon that passes just fine here in Oregon, but NOx is
too high if I have driven it for a long period and it is running at the
higher temperatures that come with long driving. If I have driven it only
6 miles at moderate speeds, it passes just fine.

By their own admission at our state testing facility, it is a bit of a
problem with NOx testing. People try to heat up their cars as much as
possible before going through the test, in order to reduce hydrocarbon,
CO, and others, which go down with high temperatures. Yet, that effort to
get the engine hot may result in excess NOx emissions.

I don't know about AZ, but here in Oregon the test is free of charge if
you aren't trying to do a renewal. If that is true there, what I would do
is have your car tested after a much shorter distance of driving than what
you have done in the past.

My guess is that the distance you drive to the testing facility is simply
too far, and the engine is too hot when you get there. On the other hand,
when you had the converter replaced, I'll bet you drove less distance to
the testing facility, and the engine was at a more normal operating
temperature then.

If there were a serious problem with the engine tuning, it would most
certainly show up in the other exhaust components.

Certainly, you should check for engine problems, but if that doesn't turn
up anything, don't be surprised. Possibly a radiator that is starting to
have a few problems might show up in elevated engine temperature, but
sometimes it is just a matter of distance driven.

Here in Oregon, last year, they didn't test cars of the age of mine for
NOx. Apparently they have decided there isn't that much that can be done
about engines of that age that are running a bit too hot, because distance
driven prior to the test is really the primary problem with causing NOx
formation.

 

formulated on Saturday :

Thanks for the suggestion! In AZ you pay about $28 for the testing, and
you get one free retest. I live about a mile from the testing facility,
so it is not too hot when I get there! I ended up going to Volvo. It
was about $100 more to have them do the cat, but it is guaranteed for 5
years...