A 1999 Camry shouldn't have any problems passing with good margin.
My guess is that the EGR valve is not working quite right. I don't know about the 1999 Camry specifically, but EGR valves are very often quite DIYable and not expensive.
NOx is Nitrous Oxide. You may have heard of vehicles with "Nitrous injection systems" where they actually have a tank of this gas aboard and inject a shot of it into the intake when they want a sudden boost in performance. This same gas is actually produced as a byproduct of buring gasoline. So, there's some of it in your exhaust gas. EGR stands for exhaust gas recirculation. This valve actually allows a bit of your exhaust gas to get back into your intake and that bit of NOx gives your car a bit of a performance boost... quite literally for free.
Nitrous oxide (N2O) is not the same as oxides of nitrogen (N0x).
Nitrous oxide is indeed used in race applications to increase horsepower output.
Oxides of nitrogen (NOx) ( the x being a variable, depending on how much oxygen is present in the combustion chamber) is a major contributor to photo chemical smog as well as acid rain.
The intent of NOx being recirculated into the intake stream of your engine by way of the EGR valve is to reduce combustion temperatures that cause NOx formation in the first place. This also slightly reduces combustion efficiency as pointed out by Cougar Allen and therefore in fact reduces performance.
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Altitude should not increase NOX emissions. Higher altitude=less oxygen=richer mixture=cooler combustion=less NOx. Most vehicles are also equipped with a barometric pressure sensor that resets to the current altitude the vehicle is at every time you shut the key off and turn it back on. The computer is programmed with different mapping tables for different altitudes and substitutes different these tables depending on readings from the baro sensor.
"Check engine light has been on for about a year. Every couple months I get it retested to see if a new code has popped up. Stays off for a few weeks then comes back on. Something about an EVAP thing, which could be a 3-way valve or a charcoal cannister. Recently a CAT code popped up as well. As long as it starts when I turn the key and drives where I need to go I'm not too worried about it at the moment. But should I be?"
An evap code is cause by something being wrong in the evaporative emissions system. The evap system is designed to prevent gas fumes from your fuel tank being expelled to the atmosphere.
Ususally a basic evap system contains a cabon canister, some vacuum lines, a vacuum solenoid, and your gas cap. The carbon canister's job is to store fuel vapors. The vacuum solenoid (usually controlled by a computer nowadays) controls when the fumes stored in the carbon canister are reintroduced to your intake so they can be burnt during combustion. This will take place when your engine is off idle and driving down the road.
ALOT (98%) of evap codes are caused by a gas cap. Either the gas cap being left loose when refueling or a defective cap. There is a one way check valve in the gas cap that allows air into the gas tank but lets nothing escape. You can test the gas cap yourself, take the cap off and suck on the part that faces the tank- you should be able to suck air through it. Now blow on the same end- you should not be able to blow through the cap. I'm willing to bet if you put a new gas cap on the car your evap code will disappear.
The CAT code you are getting could be cause by a defective converter or an oxygen sensor. There is an oxygen sensor located upstream of the converter as well as one downstream of the converter. The job of the downstream oxygen sensor is to monitor catalyst efficiency. If the catalyst in the converter becomes contaminated and doesn't do its job, the rear oxygen sensor will stop switching back and forth over the stoichiometric line and will stick rich or lean. The computer then sees this and turns on the dreaded light. If you have a defective oxygen sensor at the rear of the CAT and it is stuck reading rich or lean, the computer does the same thing and turns on the dreaded light because it can't tell the difference between a bad CAT or the bad sensor. In order to diagnose the CAT light you will need it put on a scanner and checked by a competent mechanic.
A plugged converter is usually accompanied with a loss of power. If you can't get the exhaust out the tail pipe, you can't get the next fuel/air charge into the combusion chamber. Also, keep in mind, if your converter is plugged, something caused it. You could just slap another converter on there and think everything is all good in combustionville but it will most likely end up plugged again unless you adress the underlying condition that plugged the converter in the first place.
Sorry for writing a small novel, but hey, you asked
Brad
www.AndersonKnives.ca
so I passed by, what, a hundredth of a percent?
