Volkswagen Front Wheel Drive 1974-1989 Repair Guide

CIS Fuel Injection

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CIS fuel injection vehicles can be identified by the absence of electrical connections on the fuel distributor. Also, the fuel distributor is usually painted black on these models.

IDLE ADJUSTMENT



Certain 1.8 Liter engines are equipped with a manual pre-heat valve located on the air cleaner housing. The valve is marked "S" (summer) and "W" (winter). When adjusting the idle speed, position the valve to S (unless work area is below freezing). After servicing, return the valve to the position that matches climate conditions.

Four Cylinder Engines
1976-80 MODELS

See Figure 1

  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. On some models, it may be necessary to bypass the idle stabilizer. Disconnect the plugs from the stabilizer, then connect them together.
  4.  
  5. Turn the headlamps on high beam (except 1979-80 Canadian Rabbit, Scirocco and all models equipped with an oxygen sensor). All other electrical accessories must be OFF.
  6.  
  7. Connect a tachometer to the engine. Start the vehicle and check the idle speed. Compare it to the specifications shown in the tune-up chart (in this section) or the underhood sticker.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: The idle speed adjusting screw is located on the side of the throttle body (Dasher shown)

  1. If necessary, adjust by turning the idle speed screw on the side of the throttle body. Turning the screw in reduces idle speed, turning it out increases idle speed.
  2.  

1981-84 MODELS

See Figures 2 and 3

  1. The engine must be at normal operating temperature. Make sure the ignition timing is set correctly. Read the underhood emission sticker for any special instructions which differ from these procedures.
  2.  
  3. Disconnect the crankcase breather hoses. Plug them on models through 1982. On 1983 and later models, allow hose to be opened to air. On 1982 Rabbit, Scirocco and Jetta without an oxygen sensor, disconnect the charcoal canister hose from the air inlet boot. On Quantum models, remove the plastic cap from the T-connector at the air inlet boot.
  4.  



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Fig. Fig. 2: Remove the plastic cap from the T-connector on Quantum models

  1. Disconnect the two plugs from the idle stabilizer control unit (if equipped) and connect them together. Make sure all electrical accessories are turned OFF.
  2.  
  3. Connect a tachometer to the engine. Start the vehicle and check the idle speed. Compare it to the specifications shown in the tune-up chart (in this section) or the underhood sticker.
  4.  
  5. If necessary, adjust the idle speed using the adjustment screw on the side of the throttle body.
  6.  



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Fig. Fig. 3: Idle speed adjusting screw on 1981-84 models

1985-89 EXCEPT FOX

See Figure 4

  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. Pinch off the hose leading from the idle speed boost valve(s) with a clamp. Disconnect the crankcase ventilation hoses.
  4.  
  5. On Cabriolet and Scirocco, disconnect the carbon canister hose from the T-connector on the air intake boot.
  6.  
  7. On Golf, Jetta and GTI, remove the T-connector at the air intake boot. Rotate the connector 90 degrees, then insert the blank side with the 0.059 in. (1.5mm) restrictor into the air intake boot opening. Some engines may not be equipped with this type of restrictor T-connector. This plug is available from your Volkswagen dealer as part number 026 133 382D.
  8.  



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Fig. Fig. 4: Pinch off the hose leading from the idle speed boost valve(s) with a clamp (1)-nl-> Disconnect the crankcase ventilation hoses (2 and 3)-nl-> The T-connector location (4)-nl-> The idle speed adjusting screw (5)

  1. Connect a tachometer to the engine. Start the engine and check the idle speed. Compare it to the specifications shown in the tune-up chart (in this section) or the underhood sticker.
  2.  
  3. If necessary, adjust by turning the idle speed screw on the side of the throttle body. Turning the screw in reduces idle speed, turning it out increases idle speed.
  4.  

1986-1989 FOX
  1. The engine must be at normal operating temperature. Make sure the ignition timing is set correctly. Read the underhood emission sticker for any special instructions which differ from these procedures.
  2.  
  3. Disconnect the crankcase ventilation hose.
  4.  
  5. Loosen the clamp which connects the T-connector with the restrictor to the charcoal canister, then disconnect the line.
  6.  
  7. Turn OFF all electrical accessories.
  8.  
  9. Connect a tachometer to the engine. Start the vehicle and check the idle speed. Compare it to the specifications shown in the tune-up chart (in this section) or the underhood sticker.
  10.  
  11. If necessary, adjust the idle speed using the adjusting screw located on the side of the throttle body.
  12.  

5-Cylinder Engines

See Figures 5, 6 and 7

  1. The engine must be at normal operating temperature. Make sure the ignition timing is set correctly. Read the underhood emission sticker for any special instructions which differ from these procedures.
  2.  
  3. Remove the plastic cap from the T-connector at the air intake boot.
  4.  
  5. Disconnect both crankcase breather hoses, then plug them.
  6.  



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Fig. Fig. 5: Remove the plastic cap from the T-connector



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Fig. Fig. 6: Plug the crankcase ventilation hoses after disconnecting them

  1. If equipped, disconnect both plugs at the idle stabilizer, then plug the connectors together to bypass the unit. Make sure the connectors are tight.
  2.  
  3. Turn OFF all electrical accessories.
  4.  
  5. Connect a tachometer to the engine. Start the vehicle and check the idle speed. Compare it to the specifications shown in the tune-up chart (in this section) or the underhood sticker.
  6.  



Click image to see an enlarged view

Fig. Fig. 7: Use this chart to convert a 4-cylinder tachometer reading to the actual idle speed on 5-cylinder engines

  1. If necessary, adjust the idle speed using the adjusting screw located on the side of the throttle body.
  2.  

MIXTURE ADJUSTMENT



The air/fuel mixture is measured by sampling the exhaust gas with a CO meter. If this equipment is not available, the mixture should be adjusted at a properly equipped shop.

Most models have a CO test point near the back of the engine compartment (a metal tube with a cap). Make sure the probe is a tight fit and will not draw in outside air. Others may have to be tested at the tailpipe. Always follow any special instructions on the underhood emissions label. If this label is missing from the vehicle, you should be able to order it through your local dealer. Keep in mind that ignition timing and idle speed must be correct before checking and/or adjusting the fuel mixture.

On 1981 and later models, the fuel mixture adjusting screw is covered by a tamper resistant plug to prevent adjustment of the factory setting. The mixture adjustment is not a normal maintenance or tune-up procedure on these models. Refer to Fuel System for procedures.

1976-80 Models

See Figure 8

With the engine at normal operating temperature, check the CO level at the test point. If adjustment is needed, follow these steps.

  1. Disconnect the charcoal filter hose from the air cleaner. Turn the headlights on high beam (except 1979 Canadian Rabbit/Jetta/Scirocco). On 1980 models, unplug the oxygen sensor connector (if equipped).
  2.  
  3. The removable plug covering the mixture adjusting screw has a wire loop attached to it. Remove the plug by pulling it straight up. Insert tool VW-P377 or a 3mm hex wrench in the hole. Turn the adjusting tool clockwise (in) to raise the percentage of CO and counter-clockwise (out) to lower the percentage of CO.
  4.  



Click image to see an enlarged view

Fig. Fig. 8: Mixture adjusting screw location


CAUTION
Do not push down on the adjusting tool or accelerate the engine with the tool in place.

  1. Remove the tool after each adjustment. Accelerate the engine briefly, then check the CO reading after the engine has stabilized.
  2.  

 
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