Date: Wed, 10 Aug 2011 12:29:34 -0400
Reply-To: Ken Wilford <kenwilfy@COMCAST.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Ken Wilford <kenwilfy@COMCAST.NET>
Subject: Re: Help! Hesitation on the road!
In-Reply-To: <655C31B5-8709-4AE2-A673-BAF226B3A20A@verizon.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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
>
