Date: Fri, 1 Jun 2007 11:25:39 -0700
Reply-To: David Kao <dtkao0205@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Kao <dtkao0205@YAHOO.COM>
Subject: Re: Decel Valve.....Yikes!!!
In-Reply-To: <466058CF.2040501@gmail.com>
Content-Type: text/plain; charset=iso-8859-1
This is just some thoughts. I do not own air cooled Vanagon so you decide if these
make any sense.
Bakckfiring is usually caused by fuel/air mixture too lean. Perhaps you have
a leaky intake manifold. Check the gaskets between the intake manifold and
the heads. According to Bentley the two bolts are tightented with a very small
torgue only. If the bolts are loose it will leak air from there. Just two
bolts on each head. So it's easy to check and fasten a bit.
Or somewhere between the heads and the throttle there is a leak... The main vacuum
source is coming out of the intake system. Perhaps you have a leaky vacuum up front
in the brake vacuum unit. Or perhaps you have a leaky emission component that has
a hose connected to the intake chamber. The brake vacuum unit sometimes will leak
just slightly but enough to upset the digijet system.
When small leak like that occurs the vacuum is slightly reduced which makes the
AFM to read lower air flow thus it commands the ECU to reduce fuel injection.
The mixture becomes too lean and backfires. Hope these make some sense on Friday.
David
--- vanagonvw <vanagonvw@GMAIL.COM> wrote:
> I am led to believe that my deceleration valve is a goner. Not sure if
> this is causing my backfiring, and don't quite know how to prove it, so
> I have been searching for a replacement....
>
> Seems to be, ahem, cough!, cough!, a very expensive part cough! cough!
>
> Anyone have one, know of one, or have a suggestion. I am in no position
> to spend $140 just to find out if the one I have now is causing the
> problem I am trying to solve, which is keeping me from using the van....
>
> Wow.... I thought it would be a thirty dollar part. I guess van parts
> are a lot like oil prices. Thems that have them, charge what they want,
> and those that needs them, pays it :-)
>
> I have been told I can run without it, but I don't see how that can
> work, as the engine wants to gulp lots of air when its going downhill in
> high gear, and the pedal backed off. Don't know how to make that happen
> without the valve doing its thing....
>
> Appreciate any help.
>
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