Idle Speed: Testing and Inspection
Idle Speed, Checking
NOTE:
- Idle 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 (OBD) and stored in DTC memory.
Special tools and equipment
- Scan tool VAG 1551 or vehicle system tester V.A.G 1552 with cable VAG 1551/3B
Checking conditions
- Exhaust system between catalyst and cylinder head must be free of leaks
- Coolant temperature must be at least 85 °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
- Intake air temperature less than 60 °C See display group 04, display zone 4
- No DTC must be stored in DTC memory, Diagnostic Trouble Code (DTC) memory. Refer to "Displaying and Reading Trouble Codes/With Manufacturers Scan Tool/DTC Memory Checking and Erasing" Testing and Inspection
Test sequence
- Connect scan tool VAG 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control module. Engine must be running at idle speed.
Connecting scan tool and selecting Engine Control Module (ECM). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG1551 Scan Tool" Testing and Inspection
- Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory, Diagnostic Trouble Code (DTC) memory. Refer to "Displaying and Reading Trouble Codes/With Manufacturers Scan Tool/DTC Memory Checking and Erasing" Testing and Inspection
Then:
- Leave scan tool VAG 1551 connected.
- Continue running engine at idle speed.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons 0 and 4 for function "Basic Setting" and confirm entry with Q button.
Indicated on display
Basic setting
Input display group number XXX
- Press buttons 0, 0 and 1 for "Display group number 1" and confirm entry with Q button.
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 EVAP canister purge regulator valve (N80) is closed and the air conditioner compressor switched off
- Check adjustment conditions for basic setting in display zone 4:
Specification: 1 x 111111
Significance of the number Refer to "Scan Tool Testing/Measuring Value Blocks/Evaluating Measured 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 button.
- Press buttons 0, 5 and 6 for "Display group number 56" and confirm entry with Q button.
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/Measuring Value Blocks/Evaluating Measured Value Blocks/Display Groups 30 to 49, 107 (Oxygen Sensor Control)") Testing and Inspection
- Check 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 -> button.
- Press buttons 0 and 6 for "End data transfer" function and confirm input with Q button.
If the idle speed is not obtained:
- Adapt ECM to throttle valve control module.
- Carry out test drive.
Observe the valid safety precautions when carrying out a road test.
- Again check control module DTC memory.
- Repeat idle check.
If the specifications are not obtained again:
- Check throttle valve control module. Testing and Inspection
- Check operating condition of engine. Refer to "Measuring Value Blocks/Engine Operating Mode, Check" Testing and Inspection
- Check intake air system for unmetered air. Testing and Inspection