Idle Speed: Service and Repair
Adjusting Basic Throttle Setting (S54)
Interrogate fault memory of DME control unit.
Switch off ignition.
Remove intake air manifold.
CAUTION:
Idle stops of throttle assemblies must not be altered! They have been set at the factory and secured against turning with locking paint.
Plastic caps (1) on stop screws must not be removed!
Checking basic throttle setting:
To ensure that the basic throttle setting at the 6th throttle assembly can be properly checked, you must remove protective cap (1).
Release nuts.
Remove protective cap (1) of throttle.
Remove idle-speed control valve (1) in order to gain better access to throttle assembly 2.
Release nuts, remove idle-speed control valve (1) together with holder from assembly and place to one side.
Gap between stop screw (1) and actuating lever (2) must be less than 0.05 mm.
To check gap, use a feeler gauge with a thickness of 0.05 mm. Checking gap:
- Pull pull rod on throttle actuator in throttle opening direction.
- Slide in feeler gauge (3) between stop screw (1) and actuating lever (2).
- Slowly return throttles to their stops.
Press lever (1) on throttle actuator in closing direction of throttles. In so doing, compress overload spring (2) in pull rod (3).
Release lever (1) again.
When correctly adjusted, feeler gauge will jam between stop screw (1) and actuating lever (2) and will not fall out. Perform check on each throttle assembly.
Adjusting basic throttle setting:
A readjustment must be made if the gap is larger than 0.05 mm at one or more throttle assemblies. Remove auxiliary air line.
NOTE:
In order to ensure correct throttle setting, you must slacken all the screw connections on the actuating levers with the actuating shaft except at throttle assembly 1.
It is not necessary to adjust the throttle at throttle assembly 1 because the actuating lever (1) on throttle assembly 1 is connected via set screw (3) to the actuating shaft (2). Also do not slacken screw connection of actuating lever of long pull rod with actuating shaft.
To release screw connection of actuating lever with actuating shaft, only turn nut (2) and grip screw (1).
Slacken screw connections of actuating levers with actuating shaft on throttle assemblies 2, 3, 4, 5 and 6.
Adjusting throttle assembly 2:
Move actuating lever (1) of second throttle assembly downwards until actuating lever (2) rests without play against stop screw (3).
CAUTION: Do not exert any pressure!
Tighten down screw connections of actuating levers with actuating shaft again. Observe the following instructions in so doing:
Use screws and nuts only once
- Only turn nut (2) and grip screw (1).
- For screwing down, use two open-end wrenches which should be fitted as far as possible at right angles to the actuating shaft. In this way, no torque is exerted on the actuating lever; such torque would impair the quality of adjustment.
- Tighten nut to tightening torque = 7 Nm.
Installation:
If necessary, carry out adjustment with a second person.
Adjusting throttle assemblies 3, 4, 5 and 6:
To adjust throttle assemblies 3, 4, 5 and 6, follow the same procedure as for adjusting throttle assembly 2. Carry out adjustment of throttle assemblies 3, 4, 5 and 6 in sequence. Carry out checking of basic throttle setting.
If necessary, carry out adjustment of basic throttle setting again.
Adjusting lull-load stop:
Activate servomotor via DIS Tester or MoDiC until throttles are fully open and stop screw (1) rests against detent lug.
Follow instructions in DIS Tester or MoDiC.
Carry out measurement at throttle of first throttle assembly (cylinder 1).
Adjust measurement (A) = 24.66 mm (+/-) 0.2 mm by turning stop screw.
Activate servomotor several times and check whether measurement (A) is in tolerance range.
NOTE:
Interrogate fault memory of DME control unit.
Check stored fault messages.
Rectify faults.
Then clear fault memory.
Assemble engine.