Date: Thu, 29 Jan 2004 13:02:54 -0500
Reply-To: Tim Demarest <tim.demarest@POBOX.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Tim Demarest <tim.demarest@POBOX.COM>
Subject: Re: Weird bucking
In-Reply-To: <20040129174019.36723.qmail@web13121.mail.yahoo.com>
Content-type: text/plain; charset=us-ascii; format=flowed
You may want to check your throttle switch.
I had a similar problem on my '85 because the throttle switch was staying
in the "idle" position too long, it should switch at the slightest pressure
on the throttle, and should not switch back to "idle" until the trottle is
all the way off. If it doesn't switch at the right time, the ECU will be
convinced that you are "idling" when you are actually trying to drive.
I can't get too specific on how to do this on an '84 (my '85 has a
one-year-only throttle switch assembly)... but check yer Bentley!
Tim
At 09:40 AM 1/29/2004 -0800, Damon Campbell wrote:
>In the last couple months, i've had a noticeable
>low-speed driveability problem... kind of a
>herky-jerky bucking at very light throttles. Happens
>in any gear, but is more pronounced the lower a gear
>you are in (1st being worst, 4th being not too bad).
>This typically happens around 1500-2200 rpm, and kind
>of comes and goes during a drive through town.
>
>I've had my trusty digitool on the dash looking for
>any correlation, and there is nothing i can see from
>any of the readouts. O2 is stable, AFM doesn't really
>change at all, temp sensors doing their thing
>normally... the only thing maybe kind of weird is that
>i typically show a .06v ground potential difference
>(since i have a digijet, my pin 19 is apparently a
>ground reference, or something like that). This .06v
>is always there, though, buck or not. This has
>happened with two different ECUs, too.
>
>Now, i'm wondering if it could be possible that a
>rebuilt tranny with clearances a little loose, a
>specific clutch spring stiffness (actually have that
>uber-LUK clutch bus-depot sells), a bigger motor, etc.
>could all conspire to give a natural frequency at low
>loads and certain rpms? This bucking, once it starts,
>can be attenuated by either putting in the clutch, or
>giving it a bit of gas... If the load and rpm are
>just right, the bucking can build up to be quite
>violent.
>
>How likely is this scenario? And if not, what would
>some alternate theories be? The main two variables
>include big engine and new clutch (had same rebuilt
>tranny before new engine).
>
>As always, I appreciate all your thoughts on this,
>-Damon
>
>=====
>'84 Westy (Sparky) w/2.3L WBX (wow... it actually works!)
>
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