Volkswagen Workshop Service and Repair Manuals

• ◆ Idling speed, ignition timing and Lambda factor (CO content) not adjustable.
• ◆ The idling speed is held to specification by altering the ignition timing (DIS function).
• ◆ The position of the distributor has no influence on ignition timing.
• ◆ CO content regulated by Lambda regulation. Faults in Lambda control are detected in self-diagnosis and stored in fault memory.

Special tools, testers and auxiliary items

• ◆ Fault reader V.A.G 1551 with cable V.A.G 1551/3

Test conditions

• ● Engine oil temperature min. 80 °C
• ● Electrical consumers switched off (radiator fan must not run during the check)
• ● Air conditioner switched off
• ● Exhaust system must be free of leaks
• ● No faults stored in fault memory
  , interrogating fault memory
• ● Fault reader V.A.G 1551 connected

Test sequence

• ‒ Start engine and run at idling speed.
• ‒ Operate fault reader taking into account the information on the display:
• ‒ Input 1 for "Rapid data transfer".
• ‒ Input 01 for address word "Engine electronics" and confirm with Q.
• ‒ Press ⇒ button.
• ‒ Input 04 for "Initiate basic setting" and confirm with Q.

• ‒ Input 01 for display group 01 and confirm with Q.

Note:

In the "System in basic setting" function the activated charcoal filter solenoid valve 1 (N80) is closed and the fault lamp in the dash panel lights up.

Do not continue with check until engine temperature exceeds 80 °C (display field 2).

• ‒ Briefly increase engine speed (rev. up accelerator) and then allow engine to run at idling speed for 2 minutes.
• ‒ Read off values displayed for speed, Lambda factor and ignition timing.
  Display zone 1 = Engine rpm
       Specification: 800...8801)
  Display zone 3 = Lambda factor
       Specification: 1.00 ± 0.3 fluctuating1)
  Display zone 4 = Ignition timing
       Specification: 2.25...15 <°before TDC1)

     1)     Up-to-date specifications:

=> Exhaust emissions test binder

• ‒ Press ⇒ button.
• ‒ Input 06 for "End output" and confirm with Q.

If the engine speed specifications are not attained:

• ‒ Switch off ignition.
• ‒ Check accelerator mechanism for ease of operation.
• ‒ Pull connector off Motronic control unit and then reconnect.
• ‒ Carry out test drive, interrogate fault memory and check idling speed again.