Volkswagen Air-Cooled 1970-1981 Repair Guide

Fuel Injected Vehicles

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ALL TYPE 3 AND TYPE 4; 1975 AND LATER TYPE 1 AND TYPE 2 Idle Speed



See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Tighten or loosen the idle speed adjusting screw to adjust the idle of Type 3 fuel injected models

The idle stabilizer on "Hall Effect" electronic ignitions must be bypassed before the idle is set. See electronic ignition section, above, for procedures.

The idle speed is adjusted by a screw located on the left side of the intake air distributor. To adjust the idle speed, loosen the locknut (Type 3 only) and turn the screw with a screwdriver until the idle speed is adjusted to specification. Turning the screw clockwise decreases idle speed, counterclockwise increases idle speed.

On automatic transmission Type 4 and 1975-76 Type 2 models, the idle speed regulator should also be adjusted. With the vehicle idling at 900-1,000 RPM in Park or Neutral, measure "a" in the illustration. It should be 0.020-0.040 in. If not, adjust at arrow. See Emission Controls for a test for the idle speed regulator.

If turning the screw either in or out does not noticeably affect idle speed, check for the following:

  1. Air leaks in the intake manifold system.
  2.  
  3. Air leaks into the crankcase (make sure the oil cap is on correctly).
  4.  
  5. Faulty EGR components (See Emission Controls ).
  6.  
  7. If the bypass screw must be turned fully in to lower the idle speed, or if the idle speed is fast prior to adjustment, check the auxiliary air regulator as covered in Emission Controls . If the auxiliary air regulator is OK, check the pressure regulator and deceleration valve as described in Chapter 4.
  8.  

If, after checking these systems, the bypass screw still makes little change in the idle speed, it is possible that someone has fiddled with the throttle valve adjustment screw. Refer this operation to a competent mechanic.

Idle Mixture

The idle mixture must be adjusted using an exhaust gas analyzer, a tool not usually owned by amateur mechanics; therefore idle mixture adjustment procedures are not given here. The idle mixture does not have to be adjusted unless exhaust emissions are above specified levels, the intake air sensor is replaced or after an engine overhaul.

 
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