Idle Speed: Testing and Inspection
Idling Check
NOTE:
- Idling speed, ignition timing and CO content not adjustable.
- The idling speed is regulated to specification by the throttle valve positioner in conjunction with the DIS function.
- CO content regulated by oxygen sensor control. Malfunctions in oxygen sensor control are detected in On Board Diagnostic (OBD) and stored in DTC memory.
Special tools and equipment
- VAG1551 scan tool or VAG1552 mobile scan tool with VAG1551/3B cable
Check conditions
- Exhaust system between cylinder head and catalyst free of leaks
- Coolant temperature must be at least 80 °C, See display group 04, display zone 3.
- All electrical consumers, e.g. lights and rear window heating must be switched off
- If the vehicle is equipped with an air conditioner, this must be switched off.
- On vehicles with automatic transmission selector lever in "P" or "N" position
Test sequence
- Connect VAG1551 scan tool (VAG1552). Start engine and select "Address word" 01 of engine control module. When doing this the engine must be running at idling speed. (Connecting scan tool and selecting engine control module). Refer to "VAG1551 Scan Tool Tools and Equipment
- Check DTC Memory, if necessary, repair malfunction and then Erase DTC Memory. Refer to "Displaying and Reading Trouble Codes/With Manufacture Scan Tool/Check DTC Memory (Function 02)" Testing and Inspection
- Then:
- Leave VAG1551 scan tool connected.
- Continue running engine at idling speed.
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press keys 0 and 4 for the function "Introduction of basic setting" and confirm entry with Q key.
Indicated on display:
Basic setting HELP
Input display group number XXX
- Press keys 0, 0 and 1 for "Display group number 1" and confirm entry with Q key.
Indicated on display: (1 to 4 = Display zones)
System in basic setting 1 ->
1 2 3 4
NOTE: In the "System in basic setting" function the EVAP canister purge regulator valve (N80) is closed and the air conditioner compressor switched off.
- Check the adjustment conditions for basic setting in display zone 4:
Specification: 1X111111
Significance of the numbers Refer to "Scan Tool Testing/VAG1551/Evaluating Display Group 0 to 9 (Basic Function), Testing and Inspection
- Briefly increase engine speed (rev-up) and then allow engine to run at idling speed for 2 minutes.
Checking idling speed
- Change to display group 56 as follows:
- Press C key.
- Press keys 0, 5 and 6 for "Display group number 56" and confirm entry with Q key.
Indicated on display:(1 to 4 = Display zones)
System in basic setting 56 ->
1 2 3 4
- Check the operating mode in display zone 4
Specification: 0X000 (Significance) Refer to "Scan Tool Testing/VAG1551/Evaluating Display Group 50 to 69, 99, 107 (Speed Regulation)", Testing and Inspection
- Check the specified idling speed in display zone 2.
Specification:
Manual transmission 760 RPM
Automatic transmission 700 RPM
- Check idling speed in display zone 1.
Specification:
Manual transmission 700 to 820 RPM
Automatic transmission 640 to 760 RPM
NOTE: During idling check the EVAP canister purge regulator valve and the air conditioner are switched off and the oxygen sensor control learning procedure is initiated.
- Press -> key.
- Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
If the idling speed is not obtained:
- Adapt the engine control module to the throttle valve control module, Refer to "Engine Control Module, Adapting to Throttle Valve Control Module" Service and Repair
- Carry out test drive.
Observe the valid safety precautions when carrying out a road test Technician Safety Information
- Again check the control module DTC memory.
- Repeat the idling check.
If the specifications are not obtained again:
- Check throttle valve control module. Testing and Inspection
- Check the operating condition of engine. Refer to "Scan Tool Testing/VAG1551/Engine Operating Mode Check", Testing and Inspection
- Check the intake air system for unmetered air. Refer to "Non-Trouble Code Procedures/Checking for Leaks in the Intake Air System" Testing and Inspection