Date: Tue, 12 Aug 2008 19:33:09 -0700
Reply-To: Evan Mac Donald <vanagon_dad@SBCGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Evan Mac Donald <vanagon_dad@SBCGLOBAL.NET>
Subject: Re: Digijet Idle Problems
In-Reply-To: <E367F7B7-1C4C-49C6-8600-C2C741C27F65@xochi.com>
Content-Type: text/plain; charset=iso-8859-1
An odd thing, but your van is the age for it - the throttle butterfly may be worn on the bottom, and now has a large (for idle setting purposes, anyway) gap at the bottom. Sometimes the throttle will not even fully close, if it is worn enough. It will bind, staying slightly open, adding to the gap that already appears. There were some pictures posted not so long ago of a great example of this. Maybe somebody has already posted the link.
Michael Diehr <md03@XOCHI.COM> wrote: 85 westy/1.9L/automatic -- the engine drives great -- I was running
TDC timing, but moved it to 5 BTDC and it seems happy there while
driving. I bypassed the DIS and set the idle to about 850rpm when
warm as per bentley.
However, still having trouble getting my idle to settle down -- if I
have the idle air bypass screw open enough so it doesn't die when
cold, then when warm it tends to race (up to the 1500rpm fuel
cutoff). If i have the bypass screw closed so that it doesn't do
that, then sometimes it likes to stall out.
I'm 99% sure the throttle idle switch is working properly.
Oddly, this behavior seems worse at 5btdc than at 0. (I say oddly
because it sounds like most other folks have a smoother idle with more
advanced timing).
The engine runs smooth and with good power, but idles like cr*p --
seems like it's missing and has a slow-fast-slow-fast pattern, even
when it's holding steady near 850rpm.
My theory: One of my prior mechanics drilled the AFM's adjuster
screw and may have changed that setting, back when I had vacuum leaks
and dirty injectors and a questionable ECU. So, now the engine
runs great, but idles poorly -- maybe the cause is this misadjustment?
I'm about to leave for a long trip -- any harm in playing with the AFM
adjuster screw to see if the idle will smooth out?
According to a prior post re: the function of the mystery screw:
> That screw is for adjusting the mixture at idle -- it regulates a
> small bypass that allows air to go through the AFM without being
> metered. You turn it while monitoring the CO level at the test port
> ahead of the CAT. Once the throttle opens its effect is
> swamped.