Volkswagen Front Wheel Drive 1974-1989 Repair Guide

Digifant II

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IDLE ADJUSTMENT



See Figures 1 and 2

  1. Run the engine until normal operating temperature is reached. Make sure the ignition timing is set correctly. Read the underhood emission sticker for any special instructions which differ from these procedures.
  2.  
  3. Connect a tachometer to the engine.
  4.  
  5. Make sure the idle stabilizer valve is operating. With the ignition ON (engine not running), the valve should vibrate or hum slightly.
  6.  
  7. Start the vehicle, then accelerate the engine to over 2,100 rpm at least four times. Allow the idle speed to stabilize. This cancels the hot-start idle function of the computer.
  8.  
  9. Make sure the crankcase ventilation hoses are connected and the engine oil dipstick is fully seated in its tube.
  10.  
  11. Unplug the coolant temperature sensor connector. This connector is usually blue.
  12.  



Click image to see an enlarged view

Fig. Fig. 1: Coolant temperature sensor location. The connector is usually blue

  1. Check the idle speed. It should be between 900-1000 rpm. If not, adjust the idle speed screw on the side of the throttle body until idle speed is between 925-975 rpm.
  2.  



Click image to see an enlarged view

Fig. Fig. 2: Idle speed adjusting screw location

  1. Engage the coolant temperature sensor connector. Idle speed should drop to 750-850 rpm.
  2.  

MIXTURE ADJUSTMENT



The fuel mixture is screw is plugged to prevent tampering with the factory setting. The mixture adjustment is not a normal maintenance or tune-up procedure on these models. Refer to Fuel System for procedures.

 
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