Idle Speed: Adjustments

Test conditions
- No leaks in exhaust system.
- Engine Coolant Temperature (ECT) minimum 85°C (185°F).
- Throttle valve in closed throttle position. Adjust accelerator pedal cable if necessary.
- All electrical consumers switched OFF.
- A/C switched OFF.
- Pressure measuring devices NOT connected.
- Automatic transmission vehicles: selector lever in P or N.

Checking Idle Speed

NOTE:
Idle speed cannot be adjusted.

- Connect VAG 1551 scan tool and access "Basic Setting" function of the On-Board Diagnostic system. Refer to On-Board Diagnostics, Diagnosis With Scan Tool, Address Word 01. [1][2][3][4]Description of On-Board Diagnostics

- Step through program until "Select function XX" display appears. Display will appear as shown:

Rapid data transfer HELP
Select function XX

- Check DTC memory.
^ There should be no malfunctions stored.
- If necessary, repair malfunction, erase DTC memory, stop engine (switch ignition OFF) and start again. Test drive and check DTC memory again to make sure no malfunctions are stored.
- After checking DTC memory, let engine continue to idle.

CAUTION!
^ Do not take any measurements while the radiator coolant fan is running.
^ Engine coolant temperature must be 85°C (185°F) minimum.

Display will appear as shown:

Rapid data transfer HELP
Select function XX

- Press buttons 0 and 4 to select "Basic Setting" function 04.
Display will appear as shown:

Rapid data transfer Q
08 - Read Measuring Value Block

- Press Q button to confirm input.
Display will appear as shown:

Basic Setting HELP
Input display group number XXX

- Press buttons 0, 0 and 3 to select display group 003.
Display will appear as shown:

Rapid data transfer Q
Input display group number 003

- Press Q button to confirm input.
Display will appear as shown:

Basic Setting 3
1 2 3 4.

- Read idle speed in display field 1.
^ Specified value: 700-800 RPM
- Press "arrow" button.
- Press buttons 0 and 6 to select "End Output" function 06.
- Press Q button to confirm input.

If the idle speed is too high and there are no malfunctions stored in DTC memory:
- Check Closed Throttle Position (CTP) switch.
- Check for large intake air leak.
- Check Idle Air Control (IAC) valve.
- Check learning values for Idle Speed Control (ISC).

If the idle speed is too low and there are no malfunctions stored in DTC memory:
- Check Closed Throttle Position (CTP) switch.
- Check Idle Air Control (IAC) valve.