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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
Comments: To: Calle Fallberg <calle.fallberg@SWIPNET.SE>,
          Vanagon Mailing List <vanagon@vanagon.com>
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


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