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Reading measured value block
Readout specifications for engine idling speed
Display group 02 during idling (warm engine, coolant temperature not below +85°C)
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Read measured value block 2
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◂ Indicated on display
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860 rpm
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0.0 %
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0 1 0
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88.4 °C
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Coolant temperature
▪ 85 ... 100 °C OK
▪ Less than 85 °C: => Run engine until warm
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Operating status
▪ XX1: Air conditioner signal=> switch off air conditioner
▪ X1X: Okay (idling speed switch closed)
▪ 1XX: Idling speed high because air conditioner switched on
=> switch off air conditioner
Acceleration and braking detected =>Check brake pedal switch
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Accelerator pedal position
▪ 0.0 %: OK
▪ Greater than 0.0% Sensor for accelerator pedal position incorrectly set or defective => adjust
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Engine speed
▪ 780 ... 900 rpm: OK
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Display group 13 during idling (warm engine, coolant temperature not below +85°C)
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Read measured value block 13
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◂ Indicated on display
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0.82 mg/stroke
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-0.12 mg/stroke
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0.49 mg/stroke
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No display
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Difference between injection quantities for cylinders 4/2/1 and cyl. 3
▪ -1.5 mg/stroke...+1.5 mg/stroke: OK
▪ All display zones too high: cylinder 3 strong
▪ All display zones too low: cylinder 3 weak
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Difference between injection quantities for cylinder 1 and cylinder 3
▪ -1.5 mg/stroke...+1.5 mg/stroke: OK
▪ Greater than +1.5 mg/stroke: cylinder 1 weak
▪ Less than-1.5 mg/stroke; cylinder 1 strong
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Difference between injection quantities for cylinder 2 and cylinder 3
▪ -1.5 mg/stroke...+1.5 mg/stroke: OK
▪ Greater than +1.5 mg/stroke: cylinder 2 weak
▪ Less than-1.5 mg/stroke; cylinder 2 strong
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Difference between injection quantities for cylinder 4 and cylinder 3
▪ -1.5 mg/stroke...+1.5 mg/stroke: OK
▪ Greater than +1.5 mg/stroke: cylinder 4 weak
▪ Less than-1.5 mg/stroke; cylinder 4 strong
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Notes on display group 13:
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◆ The injection system is equipped with an idling speed smooth running control function. There may be power differences between the individual cylinders (component tolerances, injector delivery rate, compression etc.) which are recognised and equalised by means of selective injected quantities during idling.
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◆ The recognition at idling speed is performed using the signal from the engine-speed sensor which delivers four signals per crankshaft revolution to the control unit. If the signals are delivered at the same rate then all the cylinders are performing equally. If one cylinder is weaker, then the crankshaft will require longer for the next half crankshaft revolution. Conversely, a more powerful cylinder accelerates the crankshaft, ensuring that less time is taken. Conversely, a more powerful cylinder accelerates the crankshaft, meaning that less time is taken.
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◆ If the control unit detects a difference, the relevant cylinder is injected with more or less fuel until the engine is running evenly again.
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◆ Using No. 3 cylinder as a reference, the measured value block displays the injected quantity adjustments that are required for the individual cylinders in order to attain an even engine idling speed.
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◆ +... mg/stroke: The cylinder in question is less powerful than cylinder No. 3 and is therefore supplied with more fuel.
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◆ -... mg/stroke: The respective cylinder is more powerful than No. 3 cylinder and is therefore supplied with less fuel.
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