Date:         Wed, 10 Aug 2011 17:54:59 -0700
Reply-To:     David Vickery <david_vickery@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Vickery <david_vickery@YAHOO.COM>
Subject:      Re: Help! Hesitation on the road!
In-Reply-To:  <4E42B1EE.7050208@comcast.net>
Content-Type: text/plain; charset=iso-8859-1

I was reading on van-cafe articles about the ground for the o2 sensor attached to the cylinder head causing problems.  What would be the symptoms of that?  I would think that in all cases, disconnecting the o2 sensor would tell you if it was the problem, because it would just run a little rich, but otherwise run fine.

I am having the same trouble as the OP with my 87.  I think it is loose grounds, or loose or intermittently bad connections with some wiring, particularly when it gets really hot outside.   I also have a suspicion about the hall sender.  It would be nice to know what the various symptoms are for different things.  My problem came on fairly suddenly, or at least got much worse quickly, so I don't think it is tune up items.  It gives a quick stumble as a warning signal, then if I keep driving it, it looses all power, and if I let the clutch in, it dies immediately.  Waiting a half hour or more, it will run again for a while.  Since it is intermitent, trying things for a short while doesn't tell me much, unless it stumbles again right away. 

--- On Wed, 8/10/11, Ken Wilford <kenwilfy@COMCAST.NET> wrote:

> From: Ken Wilford <kenwilfy@COMCAST.NET>
> Subject: Re: Help! Hesitation on the road!
> To: vanagon@GERRY.VANAGON.COM
> Date: Wednesday, August 10, 2011, 10:29 AM
> As Dennis said, this is most likely a
> problem within the oxygen sensor
> circuit.  Here is how you can know for sure.  If
> you can turn off the
> van and turn it back on and it seems to reset itself and
> run better for
> a minute or so before going back to hesitating again then
> it is
> definitely an oxygen sensor related problem.  When you
> start your van
> the computer looks at all of the sensors (Temp II, AFM,
> etc) immediately
> except for the oxygen sensor.  The computer uses a
> built in value for
> the oxygen sensor reading until so many seconds go by to
> allow the
> oxygen sensor to warm up.  So if the problem was the
> famous "Vanagon
> Bucking Syndrome" which is related to the AFM, turning the
> van off and
> back on would do nothing.  Same with the Temp II
> sensor problem.  Bad
> gas or bad fuel tank would not care about turning the
> ignition off and
> back on either.
> 
> So once you realize that your problem is coming from the O2
> sensor it
> makes troubleshooting way easier.  Now you can unplug
> the O2 sensor (big
> green wire to black wire connection in the area beneath the
> coil in the
> engine bay).  If the van runs better then you have a
> bad O2 sensor or
> bad wiring to it.  If it still runs crappy then your
> problem is most
> likely the wiring form the O2 sensor plug to the ECU
> itself.  This wire
> is a big green wire because it is actually coaxial. 
> It has a center
> signal wire surrounded by an insulator and then an outer
> braided shield
> covered by another insulator.  Sometimes the problem
> is at the very end
> of the wire.  Please cut the old plugs off and splice
> on a new one and
> mistakenly crimp the inner and outer wire together. 
> Or the end plug
> will just go bad and cause signal problems that way. 
> I would start by
> cutting the end connector off and separating the two
> wires.  If this
> fixes it then cut back the outer wire a little and try to
> crimp on a new
> end on just the center signal wire.  If messing with
> the end still
> doesn't help then you are going to have to replace the
> signal wire
> completely (which isn't that bad, but not something you
> want to do on a
> long trip).  You can just cut the signal wire at the
> ECU plug.  That
> will stop the hesitation symptoms and the van will run well
> with this
> wire cut.  It will get a gallon or two less mpg than
> it would if the
> oxygen sensor circuit was working perfectly but when this
> circuit is
> malfunctioning you will get really low mpg so cutting this
> wire will
> help those on a long trip get better mpg and no more
> bucking etc.  Then
> when you get home you can replace the wiring at your
> leisure.
> 
> To cut the wire on a 2.1l Vanagon you will need to pull the
> ECU out from
> under the rear seat then remove a phillips head screw or
> two from the
> backing of the plug.  Cut the tie wrap that holds the
> plug cover in
> place as well and the cover should come off.  Now you
> can see all of the
> ECU wiring from the engine harness.  You should be
> able to see the big
> green wire coming from the oxygen sensor and it will split
> into two
> wires a ground and the signal wire.  I believe the
> signal wire is pin 2
> for the digifant vans (confirm with Bentley before
> cutting).  I usually
> leave about an inch of the old wire coming out of the back
> of the ECU
> plug and then put a piece of electrical tape over the cut
> ends to keep
> them from touching anything.  Put it back together and
> it should fix the
> problem until you can get home and fix it for real (new O2
> sensor
> harness which we sell).
> 
> Hope this helps,
> 
> Ken Wilford
> John 3:16
> www.vanagain.com
> 
> 
> On 8/8/2011 6:27 PM, Daniel Rotblatt wrote:
> > I'm leaving Sante Fe on the return leg to L.A. The van
> is hesitating
> > while on freeway.  Momentary hesitations -
> randomly every few seconds.
> >
> > Otherwise running great.  When I had it tuned up
> it had trouble
> > starting and mechanic put in new fuel pump relay.
> >
> > Thoughts?  Just pit in gas also...was running
> fine before that.  Bad
> > gas?  Fuel pump?
> >
> > Dan
> > '85 Vanagon
> >
> > Sent from my iPhone
> >
>