Date: Sat, 17 May 2008 20:47:26 -0700
Reply-To: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Subject: Re: hesitation/bucking (was: Re: tested Oxygen Sensor, and...)
In-Reply-To: <91c8f9760805172008y472870cfp928a403aab43f084@mail.gmail.com>
Content-Type: text/plain; charset="us-ascii"
Driving with a less than perfect AFM is not likely to hurt anything else.
You have the right idea about making the contact arm rub on a new spot.
I believe you measure resistances at the AFM contacts,
And not voltages.
'changing' resistance' ....... when the arm moves, which you move with your
finger on the flapper door ......means just that- it 'changes' Changes
value.
btw.........if you know what 'accelerator pump' is in a carb....
how fast the sweeper arm moves, is what clues the ECU that the throttle has
been opened quickly, and it knows 'ok, more fuel for a second' - an
accelerator pump affect, but electronic, not a pure pump system with diagram
connected to the throttle linkage or throttle plate. The affect is the same
- more fuel for a few seconds when you command a quick rpm increase.
Just an interesting thing to grasp about it , if you find it interesting.
Be glad it's not throttle by wire !
There's no particular reason it should look dirty in there.
I read hear recently that 'Python' brand rebuilt afm's are $ 175 I think it
was.
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
pickle vanagon
Sent: Saturday, May 17, 2008 8:08 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: hesitation/bucking (was: Re: tested Oxygen Sensor, and...)
Just to send out an update on my situation:
I rechecked my vacuum hoses and replaced one of the teeny ones.
I checked the idle/deceleration switch and reset its position (it was maybe
1/2 turn off at most, seemed fine)
I checked the AFM voltages. Seemed okay, but one of the resistance specs is
"changes when you move the wiper", which isn't exactly specific, so I don't
know if how conclusive I should consider this test. Does anyone have more
specific info than what's int he Bentley on how the voltages should vary
with wiper position?
I popped the top off the AFM meter and sprayed electronics cleaner in there
and moved the wiper back and forth. I have to say, it looked really clean
inside even before I did this.
Then I drove it around a bunch today. I didn't seem to do it at all today,
but that doesn't necessarily mean its gone away. The only thing that's been
consistent about it is that it is very inconsistent! and very mild. Even if
it does come back, I can't really shell at the big bucks for another AFM
meter, unless this could actually be hurting something, rather than just a
mild annoyance.
I was thinking about moving the board in the AFM meter so that the wiper has
new track to move on. Does this basically bring the AFM meter back to
like-new condition? How tricky is this procedure?
I will probably also wire in that capacitor to the AFM meter, just in case
it might help things (or prevent future problems).
Thanks again for all the help, everyone,
Wes
On Sat, May 17, 2008 at 1:38 PM, Mike Collum <collum@verizon.net> wrote:
> pickle vanagon wrote:
>
>> I guess there is probably no test for this issue short of wiring in the
>> capacitor, correct? Would you say that my symptoms are consistent with
this
>> problem?
>>
>
> The harness and the capacitor both address what has been called "Vanagon
> Syndrome".
>
> The wiper in the AFM wipes the track somewhat hysterically (a rapid back
> and forth motion) so, when driving at a steady speed for long periods, the
> wiper motion can confuse the ECU and cause the bucking or cutting out of
the
> engine. The temporary cure is to shut off the engine and restart. What
the
> harness or capacitor do is electrically dampen those oscillations and
> prevent the problem.
>
> My '84 7 passenger exhibited what could be described as Vanagon Syndrome.
> I popped the cover off of the AFM and cleaned the track with a pencil
> eraser. The wiper had not worn completely through the track or else I
would
> have moved the board over slightly so the wiper would have new surface to
> ride on. Anyway, I did that cleaning about 6 years ago and haven't had
the
> "Symptom" again.
>
> Mike
>
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