From what you report, your O2 sensor is working fine.

G. Matthew Bulley
Bulley-Hewlett
Corporate Communications Counselors
www.bulley-hewlett.com
Cary, NC USA
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-----Original Message-----
From:   Gary McEachern [SMTP:glmce@HOTMAIL.COM]
Sent:   Wednesday, January 12, 2000 12:56 AM
To:     vanagon@GERRY.VANAGON.COM
Subject:        (LONG) Surging Idle fixed! / Surging O2 sensor readings

Hello
I'm still having a problem with the FI in my new '87 weekender. When I
first
start the van the O2 voltage starts around 0.45V and slowly climbs for
about
3-5 minutes till it reaches approx 0.8V. Once it exceeds +0.8V the voltage
starts to ramp up and down from 0 to 0.8V every few seconds.

So far this is what I've done:
1. Replaced oil, plugs, rotor and cap
2. Connected another ECU with a Digitool connected to it. This ECU
functioned the same as my ECU which makes me believe it is OK. The digitool
readings indicate the T1 and T2 sensors are in range of where they should
be. It also showed that the O2 sensor voltage was ramping up and down from
0
to 0.8V every few seconds while I was driving the van. I attributed the
ramping O2 voltage to the surging idle condition. It was nice to be able to
look at the various inputs to the ECU while I was drivinng.
My thanks to Bob Donalds for letting me use his ECU w/Digitool and also to
Darrell for creating the Digitool! It's a great diagnostic tool for the
Vanagon FI system!
3. Disconnected and replaced the idle stabilizer and valve. The surging
idle
stopped when I removed/replaced the idle stabilizer however the O2 sensor
readings continue to wildly ramp up and down.4. Exchanged the AFM and all
connected hoses with a known good parts from my other 87 van. No change to
O2 sensor readings.
The part number on the stabilizer in my vehicle is 251-907-393B. This part
number does not match the number i found on the BusDepot web site for a
1987
model. Is this the correct part number for my van?
5. Checked the fuel pressure and regulator using a SW oil pressure gauge.
Readings looked to be around 34psi at idle with vacuum connected and 40psi
with vacuum disconnected.
6. Replaced Temp II sender.  No effect.

What I haven't done yet that I can think of.
1.  Adjusted Timing
2.  Replaced O2 sensor

Questions
1. What is/are the symptom(s) of an O2 sensor going bad?
2. Could the timing affect this problem? I have not adjusted it yet.
3. The fuel pressure seems high. It should be 29/36 vs the 34/40 I read on
the oil pressure gauge I used which has poor accuracy/resolution. Should I
get a better gauge to remeasure the fuel pressure? It seems like high fuel
pressure would cause a rich condition. Do the fuel pressure regulators tend
to go bad?
4. Could a coolant leak into the cylinders cause the irratic O2 sensor
readings?

Any and all comments and suggestions are greatly appreciated.

Gary
------------------------------------------------------------
Previously I wrote:

Hello list folks

Today I found the causes for the continuous surging I was experiencing on
my
newly acquired 87 GL.
These were:
1.) Two small hoses connected that are connected to the throttle and
stabilizer valve had become disconnected on the back side of the firewall
leaving 2 sizeable vacuum leaks.
2.) The idle stabilizer control unit was bad. I disconnected the input to
the stabilizer and the idle smoothed out noticeably. I exchanged the valve
and control unit from my other van which confirmed the stabilizer control
was bad.
If anyone has a good idle stabilizer for sale please p-mail me!

While going through the troubleshooting, I disconnected the O2 sensor and
monitored its voltage with a DVM. The voltages read in the range of .8 to
.9
volts! With the same test setup the voltage off the O2 sensor on my other
van is .5V which is what I expected. I also substituted the AFM, bellows
and
associated hoses from my older van to the newer van with no effect.

>From these readings I must assume the new van is running very rich at
least
when it is not running closed loop.

What are some of the likely scenarios that would cause these high O2 sensor
voltage readings? I expected the AFM substitution to improve or correct the
problem but it made no apparent difference. Any suggestions?

Gary

Gary McEachern, Reading Ma.
'84GL Sunroof
(2) '87GL Wolfsburg Weekenders
'75 Spitfire

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