Date: Mon, 18 May 1998 08:25:13 CDT
Reply-To: Joel Walker <JWALKER@UA1VM.UA.EDU>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Joel Walker <JWALKER@UA1VM.UA.EDU>
Subject: Re: Hiccups
In-Reply-To: Message of Mon, 18 May 1998 06:42:16 +0200 from
<calle.fallberg@SWIPNET.SE>
Content-Type: TEXT/PLAIN; charset=US-ASCII
it SOUNDS like the infamous stuttering airflow meter wiper arm ... a case
where the little silver box on your air cleaner begins to vibrate at a
certain speed, and the little wiper arm inside (that moves when you move
the gas pedal) vibrates and starts sending "morse code" to the computer
(instead of a steady signal). the computer thinks the airflow meter is
broken, and goes into "limp-home" mode: when the car WILL run, but not
very well. cutting off the ignition resets the computer and everything is
fine again ... until you start cruising at a steady speed again. :(
not all buses seem to do this. but most are afflicted with it. here's the
info from the Tech Bulletins that vw sent out in the u.s. ... with some
other info from some people on the Vanagon list. :)
----------------------------------------------------------
from Service Bulletins, Model Year 1992
........................................................................
Technical Bulletin
Group: 24
Number: 92-01
Date: February 29, 1992
Subject: Vanagon Intermittent Misfire
Model(s): All Vanagon Digifant Fuel Injection Engines
CONDITION
After driving for 1/2 to 2 hours at a constant speed, vehicle
experiences lack of power, cuts-out or stalls, often accompanied by
bucking or jerking of the vehicle.
In ALL cases, the vehicle will restart immediately. This symptom may
not re-occur for several weeks/months. Inspection by the dealer results
in nothing conclusive.
Some air-flow meters may experience a vibration resonance of the
metering potentiometer wiper during extended constant driving. This
resonance causes the air-flow meter to supply an intermittent signal
to the Digifant ECU. The ECU will then default to a "no-load" condition
and reduce the injection time.
SERVICE
Harness, Part No. 025 906 302A, is available to resolve this condition.
* remove electrical connector from air flow sensor (see Figure 24-174)
* install converter assembly, Part No. 025 906 302A, between harness and
air flow sensor
NOTE
If customer complaints persist after performing the above repair,
contact your Zone Product Support Specialist (TSM in Canada).
*****************************************************************
* CAUTION *
* Part numbers are for reference only. Always check with your *
* Parts Department for latest information. *
****************************************************************
........................... end ......................................
harness costs about $100! very simple to install. takes about three
minutes maximum. the new harness fits between the old harness and the
silver air-flow meter box attached to the air cleaner box. remove the
silver clip, wiggle out the big wiring connector (from the side of the
air-flow meter), connect the proper end of the new harness to the big
big wiring connector you just wiggled out, put the new clip into the
new connection; then take the other end of the new harness and plug it
into the air-flow meter connection. put the silver clip back. and you
are done.
--------------------------------------------------------------------===
from Service Bulletins, Model Year 1992
......................................................................
Technical Bulletin
Group: 24
Number: 92-02
Date: April 30, 1992
Subject: Vanagon Driveability Complaints
Model(s): All Water Cooled Engine Vanagons
SUPERCEDES TECHNICAL BULLETIN 24-92-01 (February 29, 1992)
CONDITION
After driving for an extended period of time at a constant speed, the
vehicle may, on occasion, experience a deterioration of performance
which may be accompanied by a hestiation or surging.
In many cases, after turning off the engine and subsequent re-start or
without having taken any action, the symptoms disappear. These symptoms
may not recur for several weeks or months.
SERVICE
To resolve this condition, wire harness Part No. 025 906 302A, should be
installed. This harness provides improved signal voltage stablization.
* remove electrical connector from air flow sensor
* install wire harness, Part No. 025 906 302A, between main harness
connetion and air flow sensor connection.
*****************************************************************
* CAUTION *
* Part numbers are for reference only. Always check with your *
* Parts Department for latest information. *
****************************************************************
NOTE
When troubleshooting this system and performing continuity checks, the
following should be noted. Due to active components in the wire
harness, Part No. 025 906 302A, there is not continuity between pin two
of the connectors. The following chart on page 2 lists the resistence
of each circuit.
---------------------------------------------
Terminal Approximate
Number Resistance
---------------------------------------------
1 Zero Ohms
2 Greater than 1 Meg. Ohms
3 Zero Ohms
4 Zero Ohms
5 Zero Ohms
NOTE
If customer complaints persist after performing the above repair,
contact your Zone Product Support Specialist for assistance.
........................... end ......................................
harness costs about $100! very simple to install. takes about three
minutes maximum. the new harness fits between the old harness and the
silver air-flow meter box attached to the air cleaner box. remove the
silver clip, wiggle out the big wiring connector (from the side of the
air-flow meter), connect the proper end of the new harness to the big
big wiring connector you just wiggled out, put the new clip into the
new connection; then take the other end of the new harness and plug it
into the air-flow meter connection. put the silver clip back. and you
are done.
--------------------------------------------------------------------===
IMPORT SERVICE MAGAZINE
July '93 Vol. 6 No. 8
Subject: more 'Ghost harness' info
After driving for an extended period of time at a constant speed, some
water cooled Vanagon engines may loose performance or hesitate and surge.
In many cases, the symptoms will disappear after turning off the engine
and restarting. After that, the symptoms may not reoccur for several
weeks or months.
A new wiring harness (P/N 025 906 302A) is available to correct this
problem. The new harness provides better signal voltage stabilization
than the old harness it is designed to replace.
To install the new harness, remove the air flow sensor harness
connector. Install the new harness between the main harness
connector and the air flow sensor connector.
There are active components in the new wiring harness. For this
reason, there is no continuity between terminal number 2 at one
of the harness connectors and terminal 2 in the harness connector at
the other end of the new harness. This is normal and should not be
considered a fault.
All other connector terminals should have 0 ohms resistance from one
harness connector to its mate in the connector at the other end of
the harness. Keep this in mind when troubleshooting this system and
performing continuity checks.
From: "Dan Houg" <HOUGD@mdh-bemidji.health.state.mn.us>
------------------------------------------------------------------------=
My first experience related to the problem was when I drove on the highway on
a constant speed and after an hour or so my engine just suddenly lose all
power, and after I stop and start again it work fine , the same problem that
Derek has told about in the Technical bulletin TB#12 and TB#13 he has put
togeteher from VW information he has. I phone some friends in Sweden and
quite soon I understod that the problem was known as well as very special.
This was back in 93.
It seems like that the fault first was found in Sweden but when reported first
didn't the german compane Boch belive that it was a problem with the air flow
meter but a local VW service person use a oscilloscope to monitor the output
voltage from the resistor wiper that measure the air flow value during a long
measuring time. And his work pays off; He found out that if the engine runs
for a long time very constant and specially also when the weather type is
little frosty then the wiper could start to lose the electrical contact on the
resistor trace (It is not to easy to find the word in english, but I think you
understand what I mean) and the voltage starts to oscillate instead of have
a relative stable value.
The DIGIJET (and probely DIGIFANT) electronically box accumulate this
oscillator voltage value , but after a while it thinks it is a malfunction and
shut of the electronic pulses to that control the gasoline flow to the engine:
the engine suddenly lose all power !!. When the engine is restarted all memory
in the control box is reseted and the engine runs fine until the same
situation happens again , that can take days, weeks or may not happen again
The solution ( (if the gurantee is passed and you don't want to try the $100
version first )at least for a while ( if the air flow wiper resistance trace
is totally unconducting(worn out) then the whole air flow meter has to be
exchanged)) is to stabilize the output voltage round its oscillating average
value., The air flow box connector has four pins. Between pin 1 and 4 is the
NTC-1 resistor that measures the temperature inside the air flow meter.
Between pin 4 and 3 is the Potentiometer endpoints and pin 2 is the wiper of
the potentiometer that moves by the air flow and also is the output voltage
signal that must not oscillate. The easiest way is to add a $0.5 25 V 10 uF
tantal capacitor with its +side connected to pin 4 and its common to pin 2
(who is the air flow voltage output) to stabilise the voltage. Later Boch
came out with the $100 box that I think more or less make the same thing.
Practically I mount the capasitor on a two wire 15 cm cable that I solder on
the pin 4 and 2 (note the polarity) in the connector that mounts on the air
flow meter box on the top. and then taped so it was completely water resistant
and dust resistant.
I can only say that I have not have the problem ever since. but You never know
if this fix was the whole solution for the engine power lose. God Luck!! If
it not works , don't blame me, if it works use your other $ 99 to something
more fun!
Lars Herrnsdorf
Gottenborg Sweden
------------------------------------------------------------------------=
From: smitht@jupiter.sun.csd.unb.ca (Tim Smith)
Unsolicited endorsement, from a sample size of one vanagon: This does work,
cleared my probs immediately, so far for 14months now. My only rec. is that
when installing simply pull back the rubber boot exposing the 4 wires that
go to the connector. Find #s 2 and 4 and simply nick them for a 1/2" or so
to expose the bare copper. Pry the wire out of the insulation by pushing a
nail/knife under. Then solder the capacitor right across the bared loops of
copper. No 15cm leads, no fighting with connector lugs etc. Use some
electrical tape over the solder sites then tuck, everything neatly back
inside the rubber boot. The capacitor I used was a 25Volt 22microfarad
tantalum type. I read of mention of the stuttering problems not being
completely solved with 10ufd size, quoted from a LIMBO article (via email)
maybe?
NOTE: it says to use #2 as positive, #4 as negative !!! I used it this way.
Any electrical geeks wanna tell if it makes a diff in this application? Prolly.
Tim Smith
'87 non-stuttering Syncro