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Reading measured value block (data block)
Readout specifications for engine idling speed - vehicles with 74 kW engine
Display Group 002 at idling speed (engine warm, coolant temperature not below 75°C)
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Display group 2
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⇒
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◂ Indicated on display
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XXXX rpm
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X.X %
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X X X
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XX.X °C
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◂ Display zones 1 ... 4
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Coolant temperature 75 ... 110 °C: okay
▪ < 75 °C: => run engine till warm
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Operating status:
▪ XX1: AC compressor ON
▪ X1X: Idling speed switch closed
▪ 1XX: Increased idling speed
with AC compressor ON
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Accelerator pedal position: 0.0 % okay
▪ > 0.0 %:
▪ accelerator pedal position sender -G79 incorrectly set or defective, open circuit in wiring
▪ => test4)
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Engine speed:
▪ Manual gearbox: 860 ... 940 rpm okay
▪ Automatic gearbox: 790 ... 870 rpm okay
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4) Test accelerator pedal position sender:
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Display group 010 at idling speed (engine warm, coolant temperature not below 75°C)
Display group 013 at idling speed (engine warm, coolant temperature not below 75°C)
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Display group 13
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◂ Indicated on display
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X.XX mg/stroke
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X.XX mg/stroke
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X.XX mg/stroke
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X.XX mg/stroke
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◂ Display zones 1 ... 4
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Engine smoothness injection quantity, Cylinder 4:
-2.8 mg/stroke ... +2.8 mg/stroke okay
▪ > +2.8 mg/stroke or < -2.8 mg/stroke => Page 01-110
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Engine smoothness injection quantity, Cylinder 3:
-2.8 mg/stroke ... +2.8 mg/stroke okay
▪ > +2.8 mg/stroke or < -2.8 mg/stroke => Page 01-110
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Engine smoothness injection quantity, Cylinder 2: -2.8 mg/stroke ... +2.8 mg/stroke okay
▪ > +2.8 mg/stroke or < -2.8 mg/stroke => Page 01-110
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Engine smoothness injection quantity, Cylinder 1: -2.8 mg/stroke ... +2.8 mg/stroke okay
▪ > +2.8 mg/stroke or < -2.8 mg/stroke => Page 01-110
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Evaluation: Idling speed smooth running control display
The injection system is equipped with an idling speed smooth running control. There may be power differences between the individual cylinders (component tolerances, injector delivery, compressions etc.) which are recognised and equalized via selective injected quantities.
Recognition at idling speed is via the signal from the engine speed sender. If the signals are delivered at the same rhythm then all cylinders work the same. If one cylinder is weaker then the crankshaft takes longer for the next half revolution. Conversely a more powerful cylinder accelerates the crankshaft so less time is taken.
If the control unit recognises a difference, then the relevant cylinder is given more or less fuel, until the engine runs evenly again.
+... mg/H: The respective cylinder is less powerful and is therefore supplied with more fuel.
-... mg/H: The respective cylinder is more powerful and is therefore supplied with less fuel.
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