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 TestTroubleshooting Guide
NOTE
Refer to the Fuel System chapter for most
of DFI trouble shooting guide.
This is not an exhaustive list, giving every
possible cause for each problem listed. It
is meant simply as a rough guide to assist
the troubleshooting for some of the more
common difficulties.
Engine Doe ...
Drive Chain Slack Inspection
Refer to the Drive Chain Slack Inspection in the Periodic
Maintenance chapter.
Drive Chain Slack Adjustment
Refer to the Drive Chain Slack Adjustment in the Periodic
Maintenance chapter.
Wheel Alignment Inspection/Adjustment
Refer to the Wheel Alignment Inspection in the Periodic
Maintenance ...
Gear Position Switch Inspection
NOTE
Be sure the transmission and external shift mechanism
are good condition.
Remove the fuel tank (see Fuel Tank Removal in the Fuel
System (DFI) chapter).
Disconnect the connector [A].
Set the hand tester [A] to the × 1 kΩ or × 100 Ω range
and connect i ...