Volkswagen Golf/Jetta 2 manual

Idle speed - adjustment
Fuel and exhaust systems - K-Jetronic fuel injection - 16 valve engines / Idle speed - adjustment


1 Run the engine to normal operating temperature, then check that all electrical components are switched off. Note that the electric cooling fan must not be running during the adjustment procedure.

2 Disconnect the crankcase ventilation hose (see illustration).

2.2 Disconnecting crankcase ventilation hose
2.2 Disconnecting crankcase ventilation hose

3 Connect a tachometer and an exhaust gas analyser to the engine.

4 If the injector pipes have been removed and refitted just prior to adjustment, run the engine to 3000 rpm several times then allow it to idle for at least two minutes.

5 Check that when the ignition is switched on, the idling stabilisation control valve is heard to buzz. If not, check the system with reference to Section 3.

6 Disconnect the wiring plug for the idle stabilisation system. This is located near the ignition coil (see illustration).

2.6 Idle stabilisation wiring plug (1)
2.6 Idle stabilisation wiring plug (1)

7 Allow the engine to idle, then check that the idle speed is 1000 ± 50 rpm. If necessary, remove the cap and turn the idle speed adjustment screw as required (see illustration).

2.7 Idle speed (A) and mixture (B) screws
2.7 Idle speed (A) and mixture (B) screws

8 Check that the mixture (CO reading) is as specified. Temporarily block off the exhaust tailpipe not fitted with the analyser probe while making the check. If necessary, turn the mixture screw as required after removing its cap. A special key is necessary in order to turn the screw but a suitable tool may be used as an alternative. Note that the screw must not be depressed or lifted and that the engine must not be revved with the tool in position.

9 Refit the crankcase ventilation hose. If the CO reading increases, the engine oil is diluted with fuel and should be renewed.

Alternatively, if an oil change is not due, a long fast drive will reduce the amount of fuel in the oil.

10 Reconnect the wiring plug and remove the test instruments. Note that after reconnecting the wiring plug, the stabilisation system will return the idling to the specified speed.


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