Periodic Maintenance Procedures
If any one vacuum is not within the specification, turn in
the bypass screws until it seats fully but not tightly.
Special Tool - Pilot Screw Adjuster, E [A]: 57001-1603
Do not over tighten them. They could be damaged,
Turn out the bypass screw of the higher vacuum between
#1 [A] and #2 [B] to the lower vacuum.
Open and close the throttle valves after each measure-
ment and adjust the idle speed as necessary.
Inspect the vacuums as before.
If both vacuums are within the specification, finish the en-
gine vacuum synchronization.
If any vacuum can not be adjusted within the specification,
remove the bypass screws #1, #2 and clean them.
Remove the bypass screw [A], spring [B], washer [C] and
Check the bypass screw hole in the throttle body for car-
If any carbons accumulate, wipe the carbons off from the
hole, using a cotton pad penetrated with a high flash-point
Replace the bypass screw, spring, washer and O-ring as
Turn in the bypass screw until it seats fully but not tightly.
Do not over-tighten the bypass screw. The tapered
portion [E] of the bypass screw could be damaged.
Repeat the same procedure for other bypass screw.
Inspect the synchronization again.
If the vacuums are correct, check the output voltage of
the main throttle sensor (see Main Throttle Sensor Output
Voltage Inspection in the Fuel System (DFI) chapter).
Special Tool - Throttle Sensor Setting Adapter:
Main Throttle Sensor Output Voltage
Connections to Adapter:
Meter (+) → R (Sensor Y/BL) lead
Meter (–) → W (Sensor BR/BK) lead
DC 1.005 ∼ 1.035 V at idle throttle opening
If the output voltage is out of the range, check the main
throttle sensor input voltage (see Main Throttle Sensor In-
put Voltage Inspection in the Fuel System (DFI) chapter).
PERIODIC MAINTENANCE 2-17