Idle Speed: Testing and Inspection
IDLE SPEED, CHECKING
- Idle speed, ignition timing and CO content not adjustable.
- The idle speed is regulated by the throttle valve control module.
- The position of the distributor has no influence on ignition timing.
- The CO content is held to specification by the oxygen sensor control. Malfunctions in oxygen sensor control will be detected by On Board Diagnostic (OBD) and stored in Diagnostic Trouble Code (DTC) memory.
Special tools, testers and auxiliary items
- VAG 1551 scan tool with VAG 1551/3 adapter cable
Test conditions
- No malfunctions stored in DTC memory See checking DTC memory. Refer to "On-Board Diagnostics II With VAG 1551". Testing and Inspection
- Engine oil temperature minimum 80 °C (176 °F)
- Electrical consumers switched off (radiator coolant fan must not run during the check)
- A/C switched off
- Exhaust system must be free of leaks
Test sequence
- Engine running at idle
- Connect VAG 1551/1552 scan tool and select "Engine Electronics" address word 01. Refer to "On-Board Diagnostics II With VAG 1551". Testing and Inspection
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -4- to select "Basic Setting" function 04 and press -Q- button to confirm input.
Indicated on display
Basic Setting HELP
Input display group number XXX
- Press buttons -0-, -0- and -1- to input display group 001 and press -Q- button to confirm input.
Indicated on display (1-4 = Display fields)
System in Basic Setting 1 ->
1 2 3 4
NOTE: In "Basic Setting" function 04 the Evaporative Emission (EVAP) canister purge regulator valve -N80- is closed.
- Do not continue with check until engine temperature exceeds 80 °C (176 °F) in display field 2.
- Briefly increase engine speed (rev-up) and then allow engine to run at idle speed for 2 minutes.
- Check specifications (display fields 1-4).
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Carry out road test and repeat the check.
- Read the readiness code. If DTC memory has been erased, repair must be verified via appropriate display group See Readiness code, creating. Refer to "On-Board Diagnostics II With VAG 1551". Testing and Inspection