The computer does not retain anything after the ignition is cycled. No
memory there at all. It will always default to a base setting after
restart and allow time before looking for the O2 sensor signal. The
first step of diagnoses is to determine if the engine becomes rich or
lean. Some roughness at idle after warm up can happen from an uneven
fuel mix to the cylinders-often known as a lean miss-fire.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of George Goff
Sent: Tuesday, September 20, 2005 5:03 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: quick question - running rough after 2 minutes

In a message dated 9/20/05 1:02:11 PM, shepherdsond@METRO.DST.OR.US
writes:

<< Am I correct in thinking that this is a classic O2 sensor failure
(the
computer being
reset to default values when the ignition is cycled off and then on)? >>

No.  The computer retains the last value read at the OXS whenever the
car is
shut down unless the OXS is disconnected with the ignition off.

The conductor, and so the input, to the computer from the OXS might be
shorted to ground either internally by way of its shielding at its
connector or,
less likely, externally to the chassis.  This would cause the van to run
very
rich and evidence of this, other than extremely poor drivability, would
be large
amounts of black smoke from the exhaust.

If the car behaves as if it is running out of fuel or as if the fuel
filter
is clogged then, perhaps, it is running out of fuel or the fuel filter
is
clogged OR there is something queer about the throttle position switch.
Check the
function and set point of the off-idle throttle position switch.

George