Date: Sun, 27 Nov 2011 16:29:25 -0500
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: vanagon syndrome strikes...advice?
In-Reply-To: <oanoqkjeodq9xrhuv18ibr92.1322326191824@email.android.com>
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OK, not a myth but a miss-diagnoses and the pigtail fix is a patch. I have done much diagnosing and research on this as it first happened to me in 1989 traveling to California. After getting it home with van still under warranty VW was already aware and they did all sorts of stuff including the harness, O2 sensors, ECU's, Engine harness etc. Finally one day it acted up as I was heading home. I nursed it to the driveway and did my check voltages everywhere while it was still choking on itself. What I found was that the outer shield of the O2 sensor wire had about .3 volts between it and the chassis. Found same voltage on ground at AFM. Jumped to ground, problem cleared up. Removed jumper, came right back. Get the Bentley. Ground for this area goes go a butt connector with a number of things in the FI harness. Then a wire goes through the distributor harness and was connected at the base of the breather tower. I carefully put the meter lead on that ring terminal connector and there was the .3 volt. The screw was tight but the plastic base and road dirt I guess made for a bad connection. Turned screw, .3 volt disappeared and all is well. What I later determined is that any floating voltage on this ground reference gets added to the signal level the O2 is trying to obtain. If .5v is ideal and you get another .3 or more the ECU is really trying to maintain .8v. Now most sensors will top at about 1 volt new. Being cool or wet or tired I see most stop at .8 or .9. At this point you get the over rich condition which depending on how bad things are can cause anything from buck ing and jerking to the cloud of black smoke. Now how does the harness fix it? Basically it modifies the signal to the ECU to run the engine leaner and delay the response. So when you only get a slight run away situation it gets masked and you keep going. Similar harness fixes were also used on Golf's and Jettas.
I have yet to install the harness as a fix and to date I have only replaced two air flow meters, both were tampered with. I have replaced the ends of a lot of corrodes wiring in the harness though.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Mike B
Sent: Saturday, November 26, 2011 11:53 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: vanagon syndrome strikes...advice?
VW wouldnt have developed a wiring repair harness and installed them at their expense for a mythical problem. Yes, I have experienced it, and corrected it permanently with this harness. No myths there.
Sent from my Verizon Wireless Phone
Dave Mcneely <mcneely4@COX.NET> wrote:
>Dennis, my van exhibited exactly the symptoms that are typically described as "Vanagon syndrome." New AFM fixed it, period. Now, that is more expensive than an oxygen sensor, but replacing an oxygen sensor that was not bad would not have fixed the problem. Why do you say it is a "myth"? Folks vehicles do behave that way given certain conditions. If it is the oxygen sensor causing it, then so be it, but it was not in my case. The oxygen sensor was good.
>
>mcneely
>
>---- Dennis Haynes <d23haynes57@HOTMAIL.COM> wrote:
>> In my opinion "Vanagon Syndrome" is a myth. It always comes down to an O2 sensor or circuit problem. Capacitors and active harness gizmos may slightly max or hide it but the problem is not fixed until that O2 sensor issue is corrected.
>>
>> One thing that never gets mentioned is the O2 sensor heater. You need to make sure it is working. You need to make sure that it is not open and that near 12 volts is there with it connected. I have seen wiring issues where the plug has 12 volts with the sensor disconnected but due to a bad wire in the harness it drops off once the sensor is plugged in.
>>
>> The sensor is almost like a battery. It works via a chemical reaction. I have witnessed the sensor working fine most of the time and then during a long trip it begins to fail to produce voltage. Run away rich here we come (the Syndrome). Stop for a while and then it works OK and after some time "it's happening again".
>>
>> The sensor placement is really in a bad location. It is not in a consistently hot part of the exhaust. It is exposed to a lot of cooling air. It's sprayed-contaminated with rain, salt, road dirt and everything else coming right off that left rear tire. What were they thinking? Then we add some poor wiring that corrodes and combine some grounds and it a wonder things work at all.
>>
>> The only Vanagon uniqueness here is how often it plagues us.
>>
>> Dennis
>>
>>
>> -----Original Message-----
>> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
>> Behalf Of David Hardy
>> Sent: Friday, November 25, 2011 11:07 PM
>> To: vanagon@GERRY.VANAGON.COM
>> Subject: Re: vanagon syndrome strikes...advice?
>>
>> So a quick update...I unplugged the O2 sensor (thanks Angus) and the problem went away - so I changed out the sensor and she ran perfect all day. Maybe I had vanagon syndrome *and* bad O2 sensor...who knows...but we are back in happy camper-land.
>> Love this list...
>> David
>>
>> Sent from my Android
>>
>> John Meeks <vanagon@gmail.com> wrote:
>>
>> >David,
>> >
>> >Sounds like you've done all the right stuff to eliminate Vanagon
>> >syndrome as the cause of your problems..
>> >The first thing I thought after reading your diagnostic process was
>> >a failing catalytic converter. Could cause those symptoms when the
>> >cat gets hot.
>> >
>> >You might also check your voltages at the ECU per Bentley manual.
>> >
>> >John Meeks
>> >'91 Vanagon MV
>> >Northern Michigan
>> >
>> >Vanagon Rescue Squad
>> >www.vanagonauts.com
>> >
>> >
>> >
>> >On Fri, Nov 25, 2011 at 10:14 AM, David Hardy <david@planetmind.net> wrote:
>> >
>> >> Long story short...left Colorado for New Mexico in my new-to-me
>> >> 1990 westy Sunday, when 2 hrs into the trip on I-25 I felt the
>> >> dreaded single engine "buck" - one simple stumble, then another 20
>> >> minutes later, then another in
>> >> 10 minutes...then every few minutes or so. By the time we got to
>> >> Trinidad, she was stumbling pretty badly , but not bad enough to
>> >> stall out. stumbling was *not* accompanied by tach needle drop,
>> >> and seemed to do it when pressing accellerator after letting off.
>> >> if I pushed the clutch in during an "episode", idle would be
>> >> erratic, surging and sometimes dropping slowly to stall. hard to
>> >> say whether turning ignition off/on made it go away, as condition was very intermittent.
>> >>
>> >> Next morning replaced fuel filter and put in some injector cleaner.
>> >> One hour later down the highway, same deal.
>> >>
>> >> Got to Taos, read up and went to Radio Shack for a 22mf capacitor
>> >> and a soldering iron. Also got a new cap and rotor and a set of
>> >> spark plugs just in case. Installed the capacitor (electrolytic,
>> >> didn't have a tantalum), and put in new cap and rotor. thought all
>> >> was well...until about 2 hrs down the road from Taos to
>> >> Albuquerque, syndrome returned but a little different...this time
>> >> it was not stumbling, but hesitation - like a flat spot. pressing
>> >> accelerator to floor seemed to make it "catch" and clear the condition, but it would return 2-5 min later.
>> >>
>> >> So I got back in and cleaned the resistive pad in the AFM
>> >> w/alcohol, and loosened the screws that hold it's mounting plate
>> >> and shifted it about 1/2mm to get the wiper on a new track. Ran
>> >> perfect for about 30 minutes on highway, but then it struck again
>> >> and this time it was pretty severe hesitation - gas pedal wouldn't rev engine, no power, it would just cough.
>> >> if I let it go to idle it would stall. turning off ignition and on
>> >> again cleared it totally - for about 3 minutes.
>> >>
>> >> So I opened things up again and moved the plate back. installed
>> >> new plug wires for the heck of it. Also got a new O2 sensor, but
>> >> couldn't get the old one off. haven't had a chance to test it
>> >> yet...kind of a pain to have to drive an hour to see if something fixed it.
>> >>
>> >> So, anyone have any recommendations? Also, does anyone know where
>> >> I can get a replacement AFM in Albuquerque?
>> >>
>> >> David
>> >>
>> >> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> >> David Hardy
>> >> Planetmind Internetworks
>> >> Nedernet, Inc.
>> >> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> >>
>
>--
>David McNeely
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