Idle Speed: Testing and Inspection
Idle speed, checking
- Idle speed, ignition timing and CO content are NOT adjustable.
- Idle speed is controlled by the Throttle Valve Control Module.
- CO content is held within specification by oxygen control. Malfunctions in the oxygen control are monitored by On Board Diagnostic and any malfunctions are stored in the Diagnostic Trouble Code (DTC) memory.
Special tools and equipment
- VAG 1551/VAG 1552 Scan Tool with VAG 1551/3 adapter cable
Test conditions
- No malfunctions stored in DTC memory
- Battery voltage must be 11.5 V minimum
- Engine oil temperature 80 °C minimum
- All electrical consumers switched off (radiator fan must not run during check)
- Throttle cable adjustment OK
- A/C switched off
- Exhaust system must not have leaks
Test sequence
- Connect VAG 1551 (VAG 1552) Scan Tool. Refer to Scan Tool Testing/VAG 1551 Scan Tool Testing and Inspection
- With engine idling, press buttons -0- and -1- to select "Engine electronics" address word 01.
Display will appear as shown
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -4- to select "Basic setting" function 04.
- Press -Q- button to enter selection.
Display will appear as shown
Read measuring value block HELP
Input display group number XX
- Press -0- button twice to select "Display group number 1".
- Press -Q- button to enter selection.
Display will appear as shown (1 to 4 = Display fields)
Basic setting 1 ->
1 2 3 4
Note: The EVAP Canister Purge Regulator Valve -N80- is closed when function 04 is selected.
Do not continue with check until Engine Coolant Temperature exceeds 80 °C.
See Display field 2.
- Briefly rev engine then let idle for approx. 2 minutes.
- Check specifications
See Display fields 1 to 4.
Adapting idle speed
If droning noises or vibrations occur at idle it is possible to adjust the idling speed slightly. However, the idle speed must never be outside the range of the specifications.
Special tools and equipment
- VAG 1551/VAG 1552 Scan Tool with VAG 1551/3 adapter cable
Test conditions
- No malfunctions stored in DTC memory
- Engine Coolant Temperature 85 °C minimum, See display group 04, field 3
- Connect VAG 1551 (VAG 1552) Scan Tool. Refer to Scan Tool Testing/VAG 1551 Scan Tool. Testing and Inspection
- With engine idling, press buttons -0- and -1- to select "Engine electronics" address word 01.
Display will appear as shown
Rapid data transfer HELP
Select function XX
- Press buttons -1- and -1- to select "Login procedure" and confirm entry with -Q- button.
Display will appear as shown
Login procedure HELP
Input code number XXXXX
- Press buttons -0-, -1-, -2-, -8- and -3- to select Login code 01283 and confirm input with -Q- button.
If display appears as shown:
Data transfer fault
- Switch ignition off and repeat procedure.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -1- and -0- to select "Adaptation" function 10 and confirm entry with -Q- button.
Indicated on display
Adaptation
Feed in channel number XX
- Press buttons -0- and -1- to select channel number 1 and confirm entry with -Q- button.
Indicated on display
Channel 1 Adaptation xxx ->
xxx rpm x.xx ms x km/h idling
- Adjust idle rpm in steps of 10 rpm with following buttons:
VAG 1551: buttons 1 and 3
VAG 1552: buttons uparrow and downarrow
Indicated on display
Channel 1 Adaptation xxx ->
xxx rpm x.xx ms x km/h idling
- A value of 128 (equates to a specified engine speed of 860 rpm) is set by the factory.
- The idle speed must never be set outside the range of the specifications.
- Confirm input with -Q- button.
Indicated on display
Channel 1 Adaptation xxx Q
Store ammended figure?
- If rpm figure is correct, confirm with -Q- button.
Indicated on display
Channel 1 Adaptation xxx ->
Ammended figure is stored
- Conclude adaptation by pressing button.
- Press buttons -0- and -6- to select "End output" and press -Q- button to enter selection.
- Switch ignition off.