Dennis,

So yoiu are saying that the problem I have been having - 2.1L runs a
bit, starts missing, gets progressively rough, almost to the point of
stalling completely, then when I quickly turn the ignition off and back
on, it clears and runs smooth for a little bit, then starts all over -
that scenario is the consequence of a faulty O2 sensor circuit -
connections, continuity, bad O2 sensor.whatever - but it is in that
circuit????

I hope it is that easy. It will bring a close to a lot of aggravation I
have had this week.

BTW, I have a brand new O2 sensor, but as always connections are
suspect. But it did work just fine until I put in a new water pump!!

John Rodgers
88 GL Driver

Dennis Haynes wrote:

>The O2 sensor input is actually an input to a transistor based
>amplifier. The leakage at that junction is ~ .6 volt. Without the O2
>sensor connected to load it down, the input sees this voltage as the .5
>to .6 volt it is trying to maintain. Therefore, no further adjustment is
>made. The only time this doesn't work, is if the O2 sensor ground is
>floating higher that 0. The leakage voltage on the ground circuit gets
>added to the .6 volt and the ECU will keep enriching the mixture until
>it sees what it wants. Here comes the rich running and black smoke.
>Check those grounds. The same thing will happen if the o2 sensor lead is
>grounding through the shielded cable. This can be caused by water,
>especially road salt water getting between the layers. The O2 sensor
>reference ground is a separate wire in the FI harness. On syncros, it is
>usually connected at the base of the oil breather tower. Plastic makes
>for a lousy connection.
>
>Most engine running problems come down to the O2 circuit or the temp 2
>circuit. An easy check is to quickly turn the ignition off and back on
>while the engine is still running. If the problem goes away for 30 to 60
>seconds, the problem is the O2 circuit. If not, check the temp 2
>circuit. Hard starting , especially after the engine is warm is usually
>and bad connection on the temp 2 sensor. It is extremely rare for this
>sensor to go bad, but the connection has a lot to be desired. The
>problem is worsened because the idle stabilizer uses this same sensor.
>Of the 2 wires on this sensor, one goes to the ecu, the other is a
>ground. Add another ground here.
>
>Dennis
>
>-----Original Message-----
>From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
>Of Robert Smythe
>Sent: Wednesday, January 18, 2006 10:11 PM
>To: vanagon@GERRY.VANAGON.COM
>Subject: Re: running problems, 2.1
>
>when you disconnect the O2, sensor I figure the voltage output goes to
>zero.
>How does the Fuel injection treat this output?
>
>Robert
>90 MV
>
>
>
>