Idle Speed, Checking
Idle Speed, Checking
Special tools, testers and auxiliary items required
• (VAS5051) with (VAS5051/1)
Test requirements
• No leaks in exhaust system
• Engine coolant temperature at least 80 °C.
• Electrical accessories switched off (coolant fan must not run during the test).
• Air conditioning switched off.
• Pressure gauge not connected.
• Vehicles with automatic transmission: Selector lever in position P or N.
• The idling speed is tested during the basic setting of the engine.
• During basic setting, the solenoid valve for the evaporative emission (EVAP) canister purge regulator valve (N80) is closed and the air conditioner compressor is switched off.
• To eliminate vibration noises in case of a customer complaint, the idling speed can be adapted. Refer to => [ Adaptation ] Adaptation.
Test sequence
- Connect testing and information system (VAS5051 ). Refer to => [ VAS 5051, Connecting and Select Functions ] VAS 5051, Connecting and Select Functions and select vehicle system "01 - Engine electronics" in selection. Engine must be running at idling speed.
- Check Diagnostic Trouble Code (DTC) memory. Refer to => [ DTC Memory, Checking ] DTC Memory, Checking. There must not be any DTCs stored. If necessary, correct any DTCs and erase DTC memory. After erasing DTC memory readiness code must be regenerated. Refer to => [ Readiness Code, Generating ] Readiness Code, Generating.
- Leave engine idling.
CAUTION!
The coolant fan should not be running.
Display on (VAS5051):
- Under - 1 - select diagnostic function "04 - Basic setting".
Display on (VAS5051):
1. Enter display group max. input value = 255
- Enter "056" for "display group number 056" in zone - 2 - and confirm entry by pressing Q button.
Display on (VAS5051):
- Activate basic setting by pressing - A - button.
- Check whether engine speed in display zone - 1 - (actual speed) is within permitted tolerance range.
All models
• The engine speed in display zone 1 (actual speed) is the actual engine speed.
• The engine speed in display zone 2 (specified speed) is a theoretical value calculated by the engine control module.
• During idling, the engine control module always tries to adapt the actual engine speed to the specified engine speed.
• This means that during idling the actual engine speed must always be approximate to the specified engine speed.
• Display zones 3 and 4 are there for information but are irrelevant to the control of the engine idling speed.
- Exit function "04 - Basic setting" by pressing arrow button.
If specified value is not obtained:
- Check Diagnostic Trouble Code (DTC) memory again. Refer to => [ DTC Memory, Checking ] DTC Memory, Checking.
- If DTC memory was erased, readiness code must be re-generated. Refer to => [ Readiness Code, Generating ] Readiness Code, Generating.
If the idling speed is too high or too low and there are no DTCs recorded in the DTC memory, perform the following tests marked with a dot:
• Check intake air system for unmetered air. Refer to => [ Intake Air System, Checking ] Testing and Inspection.
• Check throttle valve control module. Refer to => [ Throttle Valve Control Module, Checking ] Throttle Valve Control Module, Checking.
• Check whether solenoid valve for Evaporative Emission (EVAP) canister purge regulator valve is continuously open. Refer to => [ EVAP Canister Purge Regulator Valve, Checking ] Testing and Inspection.
• Perform adaptation of throttle valve control module. Refer to => [ Throttle Valve Control Module, Adaptation ] Throttle Valve Control Module, Adaptation.
Significance of 5-digit readout of display group 056
