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 TestCoupling Bearing Removal
Remove:
Coupling
Grease Seal
Circlip [A]
Special Tool - Inside Circlip Pliers: 57001-143
Remove the bearing [A] by tapping from the wheel side.
Special Tool - Bearing Driver Set [B]: 57001-1129
...
Air Suction Valve Inspection
Remove the air suction valve (see Air Suction Valve Removal).
Visually inspect the reeds [A] for cracks, folds, warps,
heat damage or other damage.
If there is any doubt as to the condition of the reeds, replace
the air suction valve as an assembly.
Check the reed contact areas [B] of ...
ESD Actuator Resistance Inspection
Turn the ignition switch to OFF.
Remove the electronic steering damper unit (see Steering
Damper Removal in the Steering chapter).
Connect a digitalmeter to the ESD actuator connector [A].
Measure the ESD actuator resistance.
ESD Actuator Resistance
Connections: BK lead [1] ← ...