Just to let everyone know, my 91 Civic passed emissions with flying> colors! The new cat dropped my CO, hydrocarbon, and oxides of nitrogen> down to practically nothing. A dramatic difference! Even though carbon> dioxide levels don't count they do measure them and they were way down as> well.

Just to let everyone know, my 91 Civic passed emissions with flying> colors! The new cat dropped my CO, hydrocarbon, and oxides of nitrogen> down to practically nothing.

testy wrote:>>

If I remember correctly, CO2 is measured to indicate if there are> significant exhaust leaks in the system.

CO2 is a normal product of> burning a hydrocarbon. If the levels are too low, then it indicates> that there's a leak and that the other numbers are probably> artificially low since not all of the exhaust gasses are reaching the> test station's probe.

Just an aside...even though emissions testing is a pain I wholeheartedly> support the program. I think Maryland's plan is fair - $14 for the first> test, if you pass you're good for two years. If you fail the second test > is> free and they give you a list of troubleshooting ideas. Subsequent tests> are $14 and they end up giving you something like 6-8 months to correct > the> problem. If it still won't pass you can get a 2 year waiver if you can > show> repair receipts for at least $450. Sure it costs money, but if you pass> (like most people do) it's $14 every 2 years. A paltry sum when you> consider the benefit to the environment. If you fail you may have to > spend> a few bucks, in my case about $350. But I did get a tuneup and a new cat> out of the deal. My car's running great and I've minimized my > contribution> to air pollution. Win-win.>

Thanks again for all the help from the folks here at alt.autos.honda!>