Idle Speed: Testing and Inspection

Idle Speed Checking

NOTE:
- Idle speed, ignition timing and CO content not adjustable.
- The idle speed is regulated to specification by the throttle valve positioner in conjunction with the DIS function.
- The position of the distributor has no influence on ignition timing.
- 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
- VAG 1551 Scan Tool or VAG 1552 with cable VAG 1551/3

Check conditions
- Exhaust system between cylinder head and catalytic converter free of leaks
- Coolant temperature must be at least 80 degree 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
- Throttle cable adjustment must be OK, checking:

Test sequence
- Connect VAG 1551 Scan Tool ((VAG 1552). Start engine and select "Address word" 01 of engine control module. When doing this engine must be running at idle speed. (Connecting scan tool and selecting engine control module [1][2][3]Connecting VAG Scan Tool 1551/1552).
- Check DTC Memory, if necessary, repair malfunction and then Erase DTC Memory, checking and erasing DTC memory DTC Memory Checking and Erasing
- Then:
- Leave VAG 1551 Scan Tool connected.
- Continue running engine at idle speed.

Indicated on display

Rapid data transfer HELP
Select function XX

- Press keys 0 and 4 for 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 evaporative emission (EVAP) canister purge regulator valve 1 -N80- is closed and the air conditioner compressor switched off.

- Check setting conditions for basic settings in display zone 4:
Specification: 111111
Significance of figures Display Groups 0 to 9 (Basic Functions), Evaluation
- Briefly increase engine speed (rev- up) and then allow engine to run at idle speed for 2 minutes.

Checking idle 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 operating mode in display zone 4
Specification: 0x000 (Significance Display Groups 50 to 69 (Speed / RPM Regulation), Evaluation)
- Check specified idle speed in display zone 2.
Specification: 840 RPM
- Check idle speed in display zone 1.
Specification: 800 to 880 RPM
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.

NOTE: During idle speed check the activated charcoal filter solenoid valve and the air conditioner are switched off and the Oxygen sensor control learning procedure is initiated.

If the idle speed is not obtained:
- Adapt engine control module to throttle valve control module
- Carry out test drive.
- Again check control module DTC memory.
- Repeat idle speed check.

If the specifications are not obtained again:
- Check throttle valve control module. Testing and Inspection
- Check signals from / to air conditioner. Testing and Inspection
- Check operating condition of engine. Engine Operating Modes, Checking