Date: Wed, 28 Mar 2007 18:59:12 -0500
Reply-To: Matt Roberds <mattroberds@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Matt Roberds <mattroberds@COX.NET>
Subject: Re: O2 Sensor - situation 90' 2.1 (kinda long)
In-Reply-To: <20070328180604.XUJV640.fed1rmmtai104.cox.net@fed1rmimpi04.cox.net>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
> From: Jeff Lincoln <magikvw@GMAIL.COM>
> Date: Wed, 28 Mar 2007 11:09:37 -0500
>
> I'm guessing the lack of an O2 sensor is contributing to my poor
> running. (runs fine at start up but starts running rich and loss
> of engine power after it warms up.
Sounds about right. The computer is probably running in "open loop"
at startup - it ignores the O2 sensor until it thinks the sensor has
had enough time to heat up and start working. Then it tries to go
into "closed loop", looks for an input from the O2 sensor that isn't
there, and gets mad.
> I am planning on having someone drill a hole and weld a nut onto
> the existing exhaust pipe (where the cat usually is) and then thread
> an O2 sensor into the hole.
The "official" part for this is called an "O2 sensor bung". Hot-rod
shops have them and I imagine a good custom exhaust place would have
them as well. There are probably different threads, so you might want
to get an O2 sensor if you don't already have one and take it to the
shop so they can get a bung with matching threads. (Pulling your T-
shirt over your head and demanding T.P. is optional.)
If the threads don't turn out to match a normal bolt, you can also get
plugs with threads to fit the bungs. This might be a way to hedge
your bets - if you've got two possible locations for the O2 sensor
in mind, have two bungs welded in so you're only in the shop once.
The put the O2 sensor in one and a plug in the other, drive it, and
switch them around if you don't like the driveability or if the O2
sensor hits another part of the engine or something.
> I know that the sensor normally resides in the cat on a 2.1 but I
> figured this might work.
The O2 sensor has to be fairly warm to work, so try to get it no
further from the heads than the stock location. It doesn't have to
be touching the exhaust valves, but an inch from the end of the tail
pipe won't work very well either.
Many newer cars have heated O2 sensors - there is a little electric
heating element in the sensor to get it up to temperature quicker.
There are extra wires for the heating element. If for some reason
you can't get your O2 sensor close enough to the engine, and it has
poor driveability until you've driven it for a long way, switching
to a heated sensor might be an option. The trick will be finding
a heated one whose sensor matches the response of the stock unheated
one for your van.
> Is there really a big difference in the O2 sensors that are ready
> to plug in and the others that have to be spliced?
Click! Unplug old sensor. Plug in new sensor...click! Drink beer.
vs. Futzing around with wire splices for 15 minutes. :)
> According to something I read the the pre-wired sensors are far
> superior.
Besides the extended beer drinking time, another argument is that
the signal from an O2 sensor is rather small, and a poorly done
field splice can cause problems - either now or in the future after
water gets into it. I have seen a Bosch splice-it-yourself kit
and the splices they provide are definitely a cut above the usual
blue and red butt splices you get at the hardware store, so using
a firm hand on the crimp pliers may well give you a good connection
that will last.
Matt Roberds
