Thanks Mark...I knew that it couldn't be that simple.

There's one other thing that I noticed today while test driving - when the
power drops off the sound of the engine, or more specifically the exhaust
note, changes dramatically to a strained buzzing.  Almost sounds like the
exhaust is plugged.

Would a damaged catalytic converter act and sound this way?

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
mark drillock
Sent: Tuesday, September 27, 2005 12:56 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Losing power...update

No, merely unplugging the connectors to the O2 sensor does not eliminate
the possibility of a problem with that circuit. The ECU ignores the O2
sensor until the Temp2 sensor tell the ECU that the engine is warmed up.
Then the ECU monitors the voltage on 2 specific wires in the FI harness
that it assumes will give it the status of the O2 content in the
exhaust. There are several known types of failures of this wiring
between the ECU and the sensor. Even with the sensor unplugged at the
far end, some problems with with this wiring can give the ECU false
readings that will cause it to badly screw up the mixture as soon as the
Temp2 sensor tells it the engine is warm enough. The bad readings can
persist even with a good O2 sensor, a new O2 sensor, or an unplugged one.

Mark

Eric Unrau wrote:

>...
>So far I have tried the following:
>1)  disconnected O2 sensor and did test drive - power dropped off 5 minutes
>into drive - restart engine - everything ok for 2-3 minutes - repeat...
>...
>So, I have a couple of questions:
>1)  does my O2 sensor test prove that it is not at fault?
>2)  any other thoughts on the cause of this problem?
>
>