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 TestRocker Arm/Tie-Rod Bearing, Sleeve Inspection
NOTICE
Do not remove the bearings for inspection. Removal
may damage them.
Visually inspect the rocker arm, or tie-rod sleeves [A] and
needle bearings [B].
The rollers in a needle bearing normally wear very little,
and wear is difficult to measure. Instead of measuring,
inspect the ...
Shift Drum Assembly
Press and insert the ball bearing [A] on the shift drum [B]
until it is bottomed.
Install:
Ball Bearing [C]
Dowel Pin [D] and Shift Drum Cam [E]
Align the pin with the groove in the shift drum cam.
Apply a non-permanent locking agent to the shift drum
cam holder bolt [F].
Tight ...
Intake Air Pressure Sensor #1 Removal
NOTICE
Never drop the intake air pressure sensor #1 especially
on a hard surface. Such a shock to the sensor
can damage it.
Remove:
Air Cleaner Housing (see Air Cleaner Housing Removal
in the Fuel System (DFI) chapter)
Intake Air Pressure Sensor #1 Connector [A]
Remove the intake air ...