Idle Speed: Adjustments
ADJUSTING IDLEAdjusting Requirements:
Engine must be in perfect mechanical condition. Electric equipment must be switched off during adjustments. Adjustments must be completed as quickly as possible, to avoid excessive heat in the intake ports and consequently wrong CO values.
Adjustments must be performed with the air cleaner mounted.
1. Install adapter US 8040 and CO tester US 4492 on the test connection.
2. Disconnect plug for oxygen sensor and connect CO tester to instructions supplied with equipment.
3. Insert a suitable plug in the air hose between the air pump and blowoff switching valve.
4. Run engine to operating temperature (80 to 90° C oil temperature).
5. Turn control screw on the throttle housing until specified engine speed of 900 ± 50 rpm is reached.
Picture shows the control screw without the charging air cooler and air cleaner.
6. Check CO level. If the CO level is not within specifications, correct the adjustment on the mixture control unit. Insert Special Tool 9156 in the spring loaded wrench in the mixture control unit. Press special tool down about 18 mm to have the spring loaded wrench engage in the mixture control screw.
Turned clockwise = richer mixture.
Turned anticlockwise = leaner mixture.
CO level: 0.6 ± 0.2 % by volume.
Note: The charging air cooler, complete air cleaner and lead-sealed wrench will have to be removed, if the CO level has to be corrected on the mixture control unit.
7. After finishing adjustments, connect the oxygen sensor plug, install the air hose and screw the plug in the test connection.
Give threads of plug a thin coat of Bosch VS 140 16 Ft or Optimoly Ht.
Torque: 15 Nm (11 ft lb).