Idle Speed Setpoint/Actual Value Comparison

Note the following points with regard to evaluating the idle speed setpoints:

• The clutch must not be operated
  
• Heating switched off to ensure the engine speed is not boosted to facilitate increased heating output
  
• All electrical loads switched off, no drive stage selected and no air conditioning
  
• The values may be slightly higher if the battery is discharged
  
• The values may deviate from the setpoints if the distance covered by the vehicle (mileage) is < 1000 km
  

Ignition timing on vehicles with M52B20 engine: Basic ignition angle 3.5 to 5 degrees crank angle (M52B20 engine has no catalytic converter heating)

Ignition timing on vehicles with M52B25 and B28 engine: approx. 0 degrees crank angle (M52B25 and B28 engines are in catalytic converter heating status after idling for approx. 4 minutes. This status may be assumed earlier if the vehicle is moved beforehand.)

Scope of test of idle speed setpoint/actual value comparison

Full operational reliability of the oxygen sensor after the catalytic converter serves as the reference for ensuring the same vehicle conditions.

The following values are tested:

• Smooth running values
  
• Engine speed
  
• Ignition timing
  
• Idle air adaptation
  
• Air mass
  
• Injection duration
  
• Load signal
  
• Opening of idle speed control valve
  
• Inlet camshaft position (M52 only)
  
• Exhaust camshaft position (M52 only)
  
• Idle integrator (M43 only)
  
• Adaptation of throttle valve position (M43 only)
  
• Idle-lambda adaptation, bank 1 (bank 2 on M52 only)
  
• Partial load-lambda adaptation, bank 1 (bank 2 on M52 only)
  
• Idle adaptation deviation (M52 only)
  
• Partial load adaptation deviation (M52 only)