Idle Speed: Testing and Inspection

Idling Check

NOTE:
- Idling speed, ignition timing and CO content not adjustable.
- Idling speed is regulated to specification by engine control module.
- CO content regulated by Oxygen sensor control. Malfunctions in Oxygen sensor control are detected in On Board Diagnostic and stored in DTC memory.

Special tools and equipment
- V.A.G 1551 scan tool or 1552 scan tool with cable VAG1551/3

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
- Air conditioning switched off (if equipped).
- On vehicles with automatic transmission the selector lever must be in "P" position.
- No faults must be stored in DTC memory.

Test sequence
- Connect V.A.G 1551 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. [1][2]Reading and Clearing Diagnostic Trouble Codes
- Check DTC memory, if necessary, repair fault and then erase DTC memory.
Clearing Diagnostic Trouble Codes
Reading Diagnostic Trouble Codes

- Then:

- Leave V.A.G 1551 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
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. Display Groups 0-9 (Basic Functions)
- 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) Display Groups 50-69 (Speed / RPM Regulation)

- Check the specified idling speed in display zone 2.
Specification:
Manual transmission 780 RPM
Automatic transmission 790 to 890 RPM

- Check idling speed in display zone 1.
Specification: 730 to 890 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. Engine Control Module (ECM), Adapting to Throttle Valve Control Module
- Test drive vehicle.
- Again check the control module DTC memory.
- Repeat the idling check.

If the specifications are not obtained again:
- Check throttle valve control part. Throttle Valve Control Module, Checking
- Check the operating condition of engine. Engine Operating Conditions, Checking
- Check the intake air system for unmetered air. Intake Air System, Checking For Leaks (False/Unmetered Air)