Chevrolet TrailBlazer, Service Manual

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Carbon Monoxide
Carbon monoxide is formed when not enough oxygen is present during the combustion
process to convert carbon (C) to carbon dioxide (CO
2
). An increase in the carbon
monoxide (CO) emission is normally accompanied by an increase in the hydrocarbon (HC)
emission because of the lack of oxygen to completely burn all of the fuel mixture.
Carbon monoxide (CO) also increases the rate at which the photo chemical smog is
formed by speeding up the conversion of nitric oxide (NO) to nitrogen dioxide (NO
2
). To
accomplish this, carbon monoxide (CO) combines with oxygen (O
2
) and nitric oxide (NO)
to produce carbon dioxide (CO
2
) and nitrogen dioxide (NO
2
). (CO + O
2
+ NO = CO
2
+
NO
2
).
The dangers of carbon monoxide, which is an odorless and colorless toxic gas, are many.
When carbon monoxide is inhaled into the lungs and passed into the blood stream, oxygen
is replaced by the carbon monoxide in the red blood cells, causing a reduction in the
amount of oxygen supplied to the many parts of the body. This lack of oxygen causes
headaches, lack of coordination, reduced mental alertness and, should the carbon
monoxide concentration be high enough, death could result.
Nitrogen
Normally, nitrogen is an inert gas. When heated to approximately 2500°F (1371°C)
through the combustion process, this gas becomes active and causes an increase in the
nitric oxide (NO) emission.
Oxides of nitrogen (NO
x
) are composed of approximately 97-98 percent nitric oxide (NO).
Nitric oxide is a colorless gas but when it is passed into the atmosphere, it combines with
oxygen and forms nitrogen dioxide (NO
2
). The nitrogen dioxide then combines with
chemically active hydrocarbons (HC) and when in the presence of sunlight, causes the
formation of photo-chemical smog.
Ozone
To further complicate matters, some of the nitrogen dioxide (NO
2
) is broken apart by the
sunlight to form nitric oxide and oxygen. (NO
2
+ sunlight = NO + O). This single atom of
oxygen then combines with diatomic (meaning 2 atoms) oxygen (O
2
) to form ozone (O
3
).
Ozone is one of the smells associated with smog. It has a pungent and offensive odor,
irritates the eyes and lung tissues, affects the growth of plant life and causes rapid
deterioration of rubber products. Ozone can be formed by sunlight as well as electrical
discharge into the air.
The most common discharge area on the automobile engine is the secondary ignition
electrical system, especially when inferior quality spark plug cables are used. As the surge
of high voltage is routed through the secondary cable, the circuit builds up an electrical
field around the wire, which acts upon the oxygen in the surrounding air to form the ozone.
The faint glow along the cable with the engine running that may be visible on a dark night
is called the "corona discharge.'' It is the result of the electrical field passing from a high
along the cable, to a low in the surrounding air, which forms the ozone gas. The
combination of corona and ozone has been a major cause of cable deterioration.