Date: Thu, 11 Sep 2008 13:28:14 -0700
Reply-To: mdrillock <mdrillock@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: mdrillock <mdrillock@COX.NET>
Subject: Re: Question about temp II sensor and bad running
In-Reply-To: <4d1b79350809111159x28515277ke20f86f1db6c9b79@mail.gmail.com>
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It seems like we go around and around on this several times each year.
Just because the engine seems to run better with the O2 sensor unplugged
IN NO WAY demonstrates that there is any problem whatsoever with the O2
sensor itself. Most likely the problem is something else and all you
have done is mask the problem. Yes, it could be the O2 sensor is bad but
that is far from certain at this point.
One real possibility is you have lost the ground for the O2 sensor
signal. It is a small brown wire in the bundle that goes to the
distributor. The other wires in that bundle are for the hall unit but
the brown wire is just for the O2 logic in the ECU and not for anything
else. The brown wire normally has a ring connector on the end and it
needs a good clean connection to bare metal on the engine. It should
never share a bolt/screw with any other ground wire.
Other things, like a bad injector, can cause this same kind of symptom.
The ECU uses the reading from the O2 sensor to know whether to lean or
richen the mixture. If one cylinder has a problem that screws up the
exhaust gases, the ECU will try to get the average reading closer to
normal by adjusting the mixture of ALL cylinders. If one injector is too
rich the ECU can't tell it is just one. It will turn them ALL down. It
will keep turning them down more in a futile effort to get the average
reading fixed. If it does this far enough the engine will run like crap
or stop running. With the O2 sensor unplugged the ECU can't see the
grossly off mixture from the one bad injector so it will just use a
default setting for all injectors. This is just one example of why
disconnecting a good O2 sensor can give the illusion of improving things.
Mark
Jim Felder wrote:
> And the loser is.... the oxygen sensor and the winners are those who
> suggested that I remove it from the loop.
>
> I just went for a five minute test drive and the van drove great.
>
> Now, what's the downside of running without an O2 sensor? There must
> be one. Mileage?
>
> I think I even have a good one somewhere. I usually replace them every
> couple of years but I never knew why. I do now! The last one I took
> out is probably good and I think I saved it. In the time it takes to
> find one or buy a new one, I wanted to know if there is a danger in
> driving with it disconnected.
>
> Jim
>
> On Thu, Sep 11, 2008 at 1:46 PM, Jim Felder <jim.felder@gmail.com> wrote:
>
>> OK, here's the news: I just went out and tried it again and it
>> stumbled to a stall in about a minute.
>>
>> Then I disconnected the O2 sensor. It ran strongly for five minutes or
>> so, longer than at any other time today. Then while it was running, I
>> plugged it back in and it was dead in 30 seconds.
>>
>> I will try to repeat this again in a few minutes to confirm what I
>> think just happened.
>>
>> Jim
>>
>>
>
>
>
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