Adjust the engine idle speed periodically on the engine at normal operating temperature.
To adjust the idle speed:

Engine oil and filter change
Throtile cable playDtc “c36” (p1764), “c37” (p1765), “c38” (p1766) or “c39” (p1767): secondary
fuel injector circuit
malfunction
Detected condition and possible cause
Detected condition
Possible cause
Some failure exists in the fuel injector signal in a high
load, high revolution condition.
Injector circuit open or short.
Injector malfunction.
Ecm malfunction.
...
Clutch cable play inspection and adjustment
Inspect clutch cable play
every 6 000 km (4 000 miles, 12 months)
Inspect and adjust the clutch cable play “a” as follows.
Clutch cable play “a”
10 – 15 mm (0.4 – 0.6 In)
Lift and support the fuel tank. Refer to “fuel tank
removal and installation” in section 1g (page 1g-
9).
  ...
Injection timing description
Injection time (injection volume)
The factors to determine the injection time include the basic fuel injection
time, which is calculated on the basis of the
intake air pressure, engine speed and throttle opening angle, and various
compensations. These compensations are
determined according to ...