Idle Speed: Testing and Inspection

Idle, Checking

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. Faults in Oxygen sensor control are detected in On Board Diagnostic (OBD) and stored in Diagnostic Trouble Code (DTC) memory.


Special tools and equipment
- Scan tool VAG 1551 or vehicle system tester VAG 1552 with cable VAG 1551/3

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.
- 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 scan tool VAG 1551 (VAG 1552). 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 "VAG 1551 Scan Tool" [1][2][3][4][5]Connecting VAG 1551 Scan Tool

- Interrogate DTC memory, if necessary, repair fault and then erase DTC memory, interrogating and erasing DTC memory. Refer to "Displaying, Reading and Erasing Trouble Codes" Testing and Inspection
- Then:
- Leave scan tool VAG 1551 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: (1-4 = Display zones)


System in basic setting 1 ->
1 2 3 4


NOTE: In the "System in basic setting" function the activated charcoal filter solenoid valve 1 (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/Measuring Value Blocks/Display Groups 0-9 (Basic Functions)" 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: (1-4 = 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/Measuring Value Blocks/Display Groups 50-69 (RPM 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 - 820 RPM 1)
Automatic transmission 640 - 760 RPM 1)

1)Up-to-date specifications:


NOTE: During idling check the activated charcoal filter solenoid 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 Adjustments
- Carry out test drive.
- Again interrogate 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/Engine Operating Modes, Checking" Testing and Inspection
- Check the intake air system for unmetered air. Testing and Inspection