Idle Speed (RPM), Checking

Idle Speed (RPM), Checking

Special tools and workshop equipment required







- VAS 5051 Vehicle diagnostic, testing and information system
- VAS 5051/1 adapter

Requirements
- No leaks in exhaust system
- Coolant temperature at least 80 degrees C.
- Electrical devices 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 idle speed (RPM) cannot be adjusted.
- The idle speed (RPM) is tested during the basic setting of the engine.
- During basic setting, the Evaporative Emission (EVAP) Canister Purge Regulator Valve -N80- is closed and the air conditioning compressor is switched off.

Work sequence
- Connect vehicle diagnostic, testing and information system VAS 5051 and select vehicle system "01 -Engine electronics" in selection. Engine must be running at idle.

- Check DTC memory. There must not be any DTCs stored. If necessary, repair any DTCs and erase DTC memory. After erasing DTC memory, generate readiness code. Diagnostic Mode 03 - Read DTC Memory
- Leave engine idling.

CAUTION: The electric coolant fan should not be running.







Display on VAS 5051:
- Under -1- select diagnostic function "04 - Basic setting".







Display on VAS 5051:
1 - Enter display group
- Enter "056" for "display group number 056" in zone -2- and confirm entry by pressing - Q- button.







Display on VAS 5051:
- Activate basic setting by pressing -A- button.
- Check whether engine speed (RPM) in display zone -1- (actual speed) is within permitted tolerance range.







NOTE:
- The engine speed (RPM) in display zone 1 (actual speed) is the actual engine speed.
- The engine speed (RPM) in display zone 2 (specified speed) is a theoretical value calculated by the engine control module.
- At idle, the ECM always tries to adapt the actual engine speed (RPM) to the desired (specified) engine speed (RPM).
- This means that the actual engine speed (RPM) must always approximately match the specified engine speed (RPM) at idle.
- The display zones 3 and 4 are there for information but are irrelevant to the control of the engine at idle.

- Exit function "04 - Basic setting" by pressing <- button.

If specified value is not obtained:
- Check DTC memory again. Diagnostic Mode 03 - Read DTC Memory
- If DTC memory has been erased, generate readiness code.

If the idle is too high or too low and there are no DTCs recorded in the DTC memory, perform the following tests:
- Check intake air system for unmetered air. Testing and Inspection
- Check Throttle Valve Control Module -J338-. Throttle Valve Control Module -J338-, Checking
- Check to see if Evaporative Emission (EVAP) Canister Purge Regulator Valve -N80- is continuously held open. Testing and Inspection
- Perform adaptation of Throttle Valve Control Module -J338-. Throttle Valve Control Module -J338-, Checking

Significance of 5 digit indication of display group 056