Idle Speed: Testing and Inspection

NOTE:
- Idle speed can NOT be manually adjusted.
- Idle speed is checked during "Basic Setting" function 04. After selecting function 04, the learning values for idle speed and oxygen sensor control are relearned (idle speed and CO content are adjusted independently), refer to "Basic Setting (Function 04)". Basic Setting (Function 04)
- CO content is controlled by oxygen sensor control for a specified value. Interference within oxygen sensor control will be captured via the On Board Diagnostic system and stored in DTC memory.


Checking requirements:
- Engine coolant temperature: 85 °C (185 °F) minimum
- All electrical consumers must be switched off (A/C, rear window defroster, etc.)
- Transmission range selector lever in "P" or "N" position
- Throttle valve must be at closed throttle position (adjust accelerator pedal cable, if necessary.
- Exhaust system must be sealed leak-tight
- No pressure measuring devices connected to the system

- Check DTC memory.
- No DTCs should be stored. If necessary:
- Repair malfunction.
- Erase DTC memory.
- Stop off engine and restart.
- Test drive and, as a check, check DTC memory again.


NOTE: Erasing DTC memory resets the readiness code (as well as with address word 01, "Basic Setting" function 04 and address word 33, mode 4).


- After checking DTC memory, start engine and let idle.


CAUTION!
Do NOT run tests or record displays while the radiator coolant fan is running.


- Using VAG 1551 scan tool, select "Basic Setting" function 04, input display group number 003, and advance until the display shows "Basic Setting 3", refer to "Basic Setting (Function 04)". Basic Setting (Function 04)

Indicated on display
(1 to 4 = Display fields)


Basic setting 3
1 2 3 4


NOTE:
- Continue with test, if the engine coolant temperature exceeds 85 °C (185 °F), refer to display group 001, display field 1.
- In "Basic Setting" function 04 the EVAP canister purge regulator valve -N80- is closed, refer to "Basic Setting (Function 04)". Basic Setting (Function 04)


- Briefly increase engine speed (RPM) and then let idle for another 2 minutes
- Observe value in display field 1.
- Specified value: 650 to 750 RPM
- Push -> button.
- Press buttons -0- and -6- to select "End Output" function 06.
- Press -Q- button to confirm input.

If the specified value is not obtained:
- Check DTC memory again.

If the idle speed is too high and no DTC is found stored in DTC memory, perform the following checks:
- Check Closed Throttle Position (CTP) switch.
- Check for large quantity intake air leak.
- Check Idle Air Control (IAC) valve.
- Check learning values for idle speed control.

If idle speed is too low and no DTC is found stored in DTC memory; perform the following checks:
- Check Closed Throttle Position (CTP) switch.
- Check Idle Air Control (IAC) valve