Idle Speed (RPM), Checking

Idle Speed (RPM), Checking

Special Tools and Equipment







- VAS5051 with VAG5051/1

Test requirements:
- Exhaust system free of leaks.
Coolant Temperature at least 80 °C.
- Electrical consumers switched off (radiator fan must NOT run during test).
- A/C switched off.
- No pressure gauge connected.
- Vehicles with automatic transmission Selector lever in P or N.


NOTE:
- Idle speed cannot be adjusted.
- Idle speed is checked during basic setting of the engine.
- During basic setting, the Evaporative Emission (EVAP) canister purge regulator valve (EVAP valve -N80-) is closed and the A/C compressor is switched off


Test sequence
- Check DTC memory. There must not be any DTCs stored, repair malfunctions if necessary, erase DTC memory, switch engine off and start again, road test vehicle and check DTC memory again as a control measure.
- Let engine continue to run at idle.


WARNING!
The electric fan for the radiator must not be running.







Display on VAS5051:
- In selection -1-, click on the diagnostic function "04 - Basic setting".







Display on VAS5051:
1 - Enter display group Max. input value = 255
Select function "056" in button field -2- for "display group number 056" and press 0 button to confirm input.







Display on VAS5051:
- Check whether the engine speed in display field -1 (actual engine speed) is within the permissible specified range.

Display Group 056:

NOTE:
- Engine speed in display field 1 (actual engine speed) is the current engine speed.
- Engine speed in display field 2 (specified engine speed) is a theoretical engine speed calculated by the ECM.
- At idle, the ECM always attempts to adapt the engine speed (actual) to the specified engine speed (specified).
- This means that the engine speed (actual) must always approximately match the engine speed (specified) at idle.
- Display fields 3 and 4 provide information, but are not relevant for checking idle speed.







Display on VAS5051:
If specified value is obtained:
- End function "04 - Basic setting" by pressing <- button.

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

If idle speed is too high or low and there are no DTCs in DTC memory, the following tests (marked with dots) must be performed:
- Check for false air in intake air system.
- Check throttle valve control module.
- Evaporative Emission (EVAP) canister purge regulator valve always open, checking.
- Perform adaptation of throttle valve control module.

Significance of 5 digit indication of display group 056

Significance Of 5 Digit Indication Of Display Group 056: