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EAS27060
CHECKING THE AIR INDUCTION SYSTEM
Air injection
The air induction system burns unburned
exhaust gases by injecting fresh air (second-
ary air) into the exhaust port, reducing the
emission of hydrocarbons. When there is neg-
ative pressure at the exhaust port, the reed
valve opens, allowing secondary air to flow into
the exhaust port. The required temperature for
burning the unburned exhaust gases is
approximately 600 to 700°C.
Air cut-off valve
The air cut-off valve is controlled by the signals
from the ECU in accordance with the combus-
tion conditions. Ordinarily, the air cut-off valve
opens to allow the air to flow during idle and
closes to cut-off the flow when the vehicle is
being driven. However, if the coolant tempera-
ture is below the specified value, the air cut-off
valve remains open and allows the air to flow
into the exhaust pipe until the temperature
becomes higher than the specified value.
AIR INDUCTION SYSTEM
A. From the air cleaner
B. To the cylinder head
1. Check:
• Hoses
Loose connections → Connect properly.
Cracks/damage → Replace.
• Pipes
Cracks/damage → Replace.
2. Check:
• Reed valve "1"
• Reed valve stopper
• Reed valve seat
Cracks/damage → Replace the reed valve.
3. Measure:
• Reed valve bending limit "a"
Out of specification → Replace the reed
valve.
Reed valve bending limit
0.4 mm (0.016 in)
4. Check:
• Air cut-off valve
Cracks/damage → Replace.
5. Check
• Air induction system solenoid
Refer to "CHECKING THE AIR INDUC-
TION SYSTEM SOLENOID" on page 8-98.
7-10
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