Mixture Calibration Potentiometer: Adjustments
Check this first:^ remove fuse 13
- remove intake hose for warm air on the preheater control unit (arrows)
- remove preheater control unit with intake hose for cold air
- remove intake air boot
- remove fuel line from fuel filter to fuel distributor at fuel filter
- remove air duct to oil cooler
- remove lower air filter
- remove harness connector 3 from differential pressure regulator
- disconnect upper air filter housing fastener 1 from above
- push mixture control assembly toward engine and raise to allow access to the potentiometer trim screw
- carefully remove sealing compound from potentiometer trim screw (arrow)
- connect test adapter VW 1501 between potentiometer and potentiometer harness connector (arrow)
- switch multimeter to 2 volts DC range and connect between terminals 2 and 3 of test adapter
- switch ignition ON
- install tool VW 1348/1
NOTE: Before installing tool, pull slide 2 out to upper stop. Place tool centrally on edge of the air flow sensor. Edge 3 must point in the direction of the fuel distributor.
- push slide 2 down to stop
- rotate screw 1 until base of magnet contacts the sensor plate mounting screw (with sensor plate in rest position)
- turn VW 1348/1 adjuster screw 1 until voltage displayed on multimeter is same as voltage U2
- connect multimeter to terminals 1 and 3 of test adapter
- adjust potentiometer trim screw until voltage displayed on multimeter falls within tolerance shown on graph
If an acceptable value CANNOT be obtained by adjusting the potentiometer trim screw
- remove fuel distributor from air flow sensor assembly
- replace air flow sensor assembly including potentiometer
NOTE: NO potentiometer adjustment is necessary if the air flow sensor assembly is replaced.
If acceptable values ARE obtained according to graph
- reinstall mixture control assembly and recheck the potentiometer
If OK
- apply sealing paint to potentiometer trim screw
For vehicles with California control unit ONLY
- erase fault memory