When the engine is running, the air intake valve is lifting up.
If the valve does not operate properly, check the air intake solenoid valve hoses for leak.
If there are no leaks, check the air intake solenoid valve.

Air Intake Solenoid Valve Unit TestFuel Injector Fuel Line Inspection
Remove:
Fuel Tank (see Fuel Tank Removal)
Air Cleaner Housing (see Air Cleaner Housing Removal)
Disconnect:
Primary and Secondary Fuel Hoses (see Fuel Hose Replacement
in the Periodic Maintenance chapter)
Do not remove the nozzle assy from the air cleaner housing.
Be sure to pla ...
Special Tools and Sealant
Oil Pressure Gauge, 5 kgf/cm²:
57001-125
Hand Tester:
57001-1394
Needle Adapter Set:
57001-1457
Extension Tube:
57001-1578
Fuel Pressure Gauge Adapter:
57001-1593
Fuel Hose:
57001-1607
Measuring Adapter:
57001-1700
Liquid Gasket, TB1211:
56019-120
...
Intake Air Pressure Sensor #2 Input Voltage Inspection
NOTE
Be sure the battery is fully charged.
Turn the ignition switch to OFF.
Remove the air cleaner housing (see Air Cleaner Housing
Removal in the Fuel System (DFI) chapter).
Disconnect the intake air pressure sensor #2 connector
and connect the measuring adapter [A] between these
con ...