Periodic Maintenance Procedures
Start the engine and warm it up thoroughly.
Check the idle speed, using a highly accurate tachometer
1 100 ±50 r/min (rpm)
If the idle speed is out of the specified range, adjust it with
the adjusting screw (see Idle Speed Adjustment).
Do not measure the idle speed by the tachometer of
the meter unit.
While idling the engine, inspect the throttle body vacuum,
using the vacuum gauge [B].
Throttle Body Vacuum
Standard: 40.7 ±1.3 kPa (305 ±10 mmHg) at idle speed
If any vacuum is not within specifications, first synchro-
nize the balance of the left (#1, #2 throttle valves) and
right (#3, #4 throttle valves) assemblies.
#1: 260 mmHg
#2: 300 mmHg
#3: 250 mmHg
#4: 280 mmHg
With the engine at the correct idle speed, equalize higher
vacuum of #1 or #2 (for example 300 mmHg) to higher
vacuum of #3 or #4 (for example 280 mmHg) by turning
the center adjusting screw [A].
After adjustment, the final vacuum measurement be-
tween the highest throttle valves may not be 290 mmHg
(for example). The goal is to have the highest two vac-
uums between the left (#1 and #2) and right (#3 and #4)
banks be the same.
Open and close the throttle after each measurement, and
adjust the idle speed as necessary.
Once the throttle valves have been synchronized, inspect
output voltage of the main throttle sensor to ensure proper
operation (procedure is explained at the end of this sec-
PERIODIC MAINTENANCE 2-19