Date:         Thu, 8 May 1997 12:45:17 -0500 (CDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         cmoran@cswnet.com (Colin A Moran)
Subject:      Idle test for digifant.

     I have compiled a series of steps from Bentley to trouble shoot the
idle function of the digifant FI.  This is taken directly out of my copy of
the repair manuel, plus some of my own observations.  I have included
references to the applicable sections of the manuel.  I noticed that there
have been several people with idle problems.  I used this test to repair my van.
  
     I used a Craftsman engine analizer to measure the RPM and a Fluke
digital multimeter to measure the switches and valve.  You realy only need
the multimeter, use the dash tach to monitor RPM.
     The first item is a few cautionary notes.
1.  Disconnect wires to O2 sensor only with the ingnition off
2.  Do not replace ignition coil with a conventional type coil
3.  Do not disconnect battery with engine running
4.  Do not applie voltage to control unit to simulate output signals.

The first area to check is timing.  It should be between 3 to 7 deg before
top dead center.  5+-1deg BTDC.  I used a timing light and the marks on the
pulley to set my timing.  Refer to Bently page 28.42

1.  Warm engine to 176 deg F
2.  Shut off engine and connect timing light to #1 cylinder.  #1 is on the
passenger side toward the front.
3.  Mark the notch on the crank pulley with white paint.  It makes it easier
to see.
4.  Loosen the clamp on the base of the distributor.  check to see that it
will turn.
5.  Disconnect temp sender with two wires located on the thermostat housing.
6.  Increase RPM to 2000 to 2500 rpm using the throttle.  I use a set of
feeler guages stuck between the throttle stop and the adjusting screw.
7.  Line-up the notch on the pulley with the seperating line of the engine
case.  Turn the distributor to move the mark.  Be careful of the belts and
the high voltage wires.  This will set the correct timing.
8.  Shut off engine and reconnect temp sensor.
9.  Tighten the distributor clamp.
10.  Remove the timing light.

The next area is the idle stabilization control.  Refer to Bently page 24.48
1.  The control unit is located on the passenger side ot the engine bay.  It
is behind the plastic cover where the air intake comes out of the body. 
2.  Remove the water trap from teh air box and the plastic cover,  there is
a screw between the water trap and plastic cover.
3.  Remove the spring clips that hold the plastic cover to the body.  Pull
the plastic cover out, it will only come out a couple of inches.  Remove
the hose on the back of the cover, its held on with a spring clamp.
4.  The control unit will be toward the front of the van it is about 4" by
5" by 1" with a multiwire connector.  The connector just slides into its mount
5.  Remove the control unit from the multiwire connector, and check for
corrosion.  My terminals where green.  Use contact cleaner to remove
the corrosion.  Install and remove the cotrol several times to ensure a good
connection.
6.  Reverse steps 1 thru 4 to reassemble.

Next you will need to test the throttle position switch.  This requires the
use of a multimeter, set to read resistance.  The engine should be off.
Refer to Bently page 24.58
1.  Unplug the connector located between cylinders 1 and 3 on the passenger
side of the engine.  It is down close to the engine block.
2.  connect the multimeter to the wires going to the switch.  The switch is
located under the throttle valve.  
3.  Open the throttle valve wide open, the switch should close and show a
reading of zero to 1.0 ohms.
4.  Allow the throttle valve to close slowly and watch the meter, the switch
should reopen a little way after wide open.  Continue to close the
throttle valve, just before it is completely closed the switch should close
again.  If the switch fails to close it needs to be adjusted.  Check the
throttle stop adjusting screw, it should have red sealer on the threads.  If
the sealer is broken or it looks like someone has tried to adjust the
screw you will have to reset it.  First turn the adjusting screw counter
clockwise until it is not touching the stop.  Then turn it in until the
screw         just touches the stop. Use a piece of paper to check it with,
tighten the screw until it will  grip a piece of paper. Turn the screw 1/2
turn more. 
5.  To adjust the switch first loosen the fixing bolt it is a small allen
headed bolt on the left of the switch plate.  The bolt on the right is the
switch      adjustment.  There is a picture of this on page 24.58 and 24.59
of the Bentley.  Place a 0.8mm feeler guage in between the throttle stop and
the throttle adjusting screw.  Turn the Switch adjusting bolt
counterclockwise untill the switch closes.  Tighten the switch fixing bolt.
6.  Disconnect multimeter and reconnect throttle switch.

Next you will need to check the idle stabilizer.  Refer to Bentley page 24.53
1.  With the ignition on the stabilizer valve should vibrate and hum.  If
not check for continuity through valve.  place multimeter on valve plug
contacts, the meter should read a low resistance.  A high resistance 200
ohms or more would indicate a bad valve.
2.  Remove crankcase breather hose and close tightly.
3.  Connect the multimeter in series with the valve so that it will read currant
4.  Start engine and let it idle.
5.  Readings should be 430+- 20 mA (fluctuating)
6.  Disconnect the  stabilizer wire just above the thermostat housing it is
a single connector with white wires.
7.  The reading should be 430 +-10mA  and should be constant.
8.  Reconnect stabilizer wire and remove multimeter from stabilizer valve.
Reconnect cranckcase breather hose.

Next you will need to set the idle speed.  Refer to Bentley page 24.50
1.  With the engnie off disconnect the O2 sensor.
2.  The engine should be warmed up to 176 deg F
3.  All electrical consumers shouold be off
4.  Remove crankcase breather hose from oil vent and seal hose tightly
5. Start engine and allow to idle, idle speed should be 880 +-50 rpm
6.  If idle is still to high use adjusting screw on throttle valve to
decrease idle speed, turn clockwise to decrease, counterclockwise to increase.
7.  Shut engine off and reconnect O2 sensor and cranckcase breather. 
8.  Restart engine and check idle speed. it should be 880+-50rpm and not
fluctuate.

     At this point my idle was back to normal. There are more test for each
component.  The pages listed above should help guide you in your test if
futher testing is needed.  Also read the archives.  There are other test,
people have come up with to help isolate the idle problem. As I found out
there are many things that can affec idle speed.

     I hope this helps , if anyone needs any  help or has a comment on the
test please feel free to drop me a line.