Idle Speed: Testing and Inspection

Idling Speed, Checking

Special tools and equipment







- VAS5051 with VAS5051/1

Test requirements:
- No leaks in exhaust system
- Coolant temperature at least 80 degree 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.

NOTE:
- The idling speed is checked 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.

Test sequence
- Connect testing and information system VAS5051 and select vehicle system "01 - Engine electronics". Engine must be running at idling speed.
- Check Diagnostic Trouble Code (DTC) memory. 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.
- Leave engine idling.

CAUTION: The electric 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.

Display Group 056:

NOTE:
- 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 <- button.

If specified value is not obtained:
- Check Diagnostic Trouble Code (DTC) memory again.
- If DTC memory was erased, readiness code must be re-generated.

Continued

If the idling speed is too high or too low and there are no DTCs recorded in the DTC memory, carry out the following tests:

- Check intake air system for unmetered air.
- Check throttle valve control module.
- Check whether solenoid valve for Evaporative Emission (EVAP) canister purge regulator valve is continuously open.
- Perform adaptation of throttle valve control module.

Significance of 5-digit readout of display group 056