Pass automotive emissions tests

Do you live in an area where your car must meet inspection requirements? Normally, your vehicle will also have to meet emissions requirements. This article will help explain what emissions are and how to troubleshoot a potential problem your vehicle may have.

Emissions are simply the exhaust gases or the remains of combustion that come out of your vehicle’s engine. An emissions test is normally done with a probe placed in the tailpipe. The emissions sampler will “sniff” or sample the contents of the exhaust coming out of the tailpipe. Every road vehicle produced has certain cleanliness requirements that it must meet. The EPA specifies this requirement to limit the amount of pollutants coming out of the vehicle.

Most emissions samplers are five gas analyzers. That means they “see” or measure five types of gases. The five gases to be measured are HC, NOX, O2, CO and CO2. We will start with HC or hydrocarbons. HCs are simply another term for the unburned fuel that goes through the engine and out the exhaust. HCs cause smog and are not good for breathing. NOX stands for nitrogen oxides. NOX is a product of highly heated and compressed air that contains nitrogen. NOX is another bad emission to breathe at high levels. The O2 remains on top of the unburned oxygen in the exhaust. Although O2 is obviously not bad, it is tested to look for people trying to cheat on the test.

The percentage of oxygen in the exhaust will also indicate the fuel ratio of the engine while it is running. CO and CO2 is carbon monoxide and carbon dioxide. CO is odorless and will give you headaches and eventually kill you by robbing your body of O2, if it is in large amounts. CO2 is present in the air, but large amounts contribute to global warming. Before doing any emissions tests the check engine light should come on soon, it should never come on or it will cause the car to fail. HCs are usually the worst problem for cars that will have to pass the test.

Many things can cause high HC, such as too much or even too little fuel, all cylinders not firing, advanced timing, faulty catalytic converter, or a non-functioning air pump. These are the most common causes. Adjustments can prevent most emissions problems. NOX is generally worse in higher compression engines. All engines produce NOX, but the use of EGR valves will cool and slow the rate of combustion of the engine’s combustion. This considerably reduces the NOX values.

O2 levels are controlled by the correct fuel ratio from fuel injection. If there is an exhaust leak, all test numbers will be low and wrong except high O2 numbers which will void the test. CO has to do with the efficiency of burning in the engine and is also greatly affected by the fuel to air ratio of the engine. CO2 is also an indicator of the configuration of the engines. HCs and NOX are by far the biggest problem areas. Catalytic converters scrub or clean most emissions and need to be replaced when they break down internally causing a loss of power and no longer clean the air.

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