[Diy_efi] O2 says rich, car runs lean..

Wed Jun 14 04:23:30 UTC 2006

On Tue, 13 Jun 2006 21:01:40 -0700 (PDT), David Rowley wrote...

O2 placement... The sensor needs to be mounted no lower than parallel
with the ground. It must be before any cats and after any turbos. As for
how much of the tip is directly in the exhaust stream I've never really
found that much of a difference. You may be able to use a zip-cut wheel
on a grinder to make your bung shorter if you think it's a big issue but
that's dicy for getting a good seal afterwards and you will need to run
a tap through the hole. A good quality M18x1.5 tap is expensive.

-Michael

> I was looking at the O2 tonight and the bung is welded on the outside
> of the header collector.  It doesn't look like the O2 is sticking very
> far into the exhaust stream.  If the O2 tip is not out into the
> exhaust flow, would this cause it to give it rich reading?  I put a
> DVM on the O2 (with the negative lead attached next to the O2 sensor)
> and found that when cold, the O2 sensor voltage measure about .450
> volts.  As it heats up, the voltage increases to about .875 volts.  If
> I introduce air (undoing the PCV hose), the reading does not change. 
> I tried this again with another new O2 sensor and got the same result.
> 
> Is the O2 tip somehow shielded from the exhaust flow causing it always
> read rich?
> 
> Thanks,
> 
> Dave
> 
> 
> Daniel Nicoson <A6intruder at myo-p.com> wrote:
> The local parts guy won't have this device.
> 
> The wide band sensors being referred to that also have NB output are
> aftermarket units that have their own controller circuit (box).
> 
> All wide band sensors have their own corresponding control circuit.
> 
> Google "Wide Band O2"
> 
> You should see most of the offerings with that search.
> 
> For a very good technical discussion of all the considerations of NB &
> WB systems, find the Megasquirt web site and look for their
> dissertation on the subject of oxygen sensors. Pretty involved the way
> those guys do a project.
> 
> Happy reading.
> 
> Dan Nicoson
> 
> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org
> [mailto:diy_efi-bounces at diy-efi.org]On Behalf Of David Rowley
> Sent: Monday, June 12, 2006 11:48 PM
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] O2 says rich, car runs lean..
> 
> First al all, I want to thank everyone for their inputs. I very much
> appreciate the help.
> 
> I have never heard of a wide band O2 that also has narrow band output.
> How does this work? Are there two different wires to select from for
> output? Under what part number and whom would I find one?
> 
> I like the idea of trying this, but I have no idea how I would explain
> what I want to the local counter person at the car parts place.
> 
> Thanks,
> 
> Dave
> 
> 
> Michael Richards wrote:
> On Sun, 11 Jun 2006 15:45:28 -0700 (PDT), David Rowley wrote...
> 
> First of all I have to say that tuning with a narrow band O2 sensor is
> useless. I've been tuning for almost 7 years not and have to
> constantly educate people about the inaccuracies of narrowband
> sensors.
> 
> Second, your readings may be related to the position of the O2 sensor.
> If you overheat a narrowband they will frequently read rich when in
> fact you're running lean. This too can sometimes be caused by an
> ignition timing issue too much retard will over heat the sensor as
> well. If you accidentally put it after a cat then that too will cause
> incorrect readings.
> 
> My suggestion is to replace the narrow band with a wideband that also
> has a narrow output. This way you can have a proper temp-compensated
> and accurate O2 reading converted to narrow band plus have a proper
> mixture display on the dash. The 383 should like somewhere in the 13:1
> under power and should run just fine in the low 15's under cruise. If
> you properly balance all 8 cylinders with a pyrometer you can run it
> leaner without any ill effects for fuel economy.
> 
> -Michael
> 
>> I have a chevy 383 motor with Vortec Heads, GMPP hot cam (218-228
>> duration, roller), Edelbrock RPM Air gap manifold and a Holley 670
>> throttle body injection unit.
>> 
>> I have a problem where the car runs and idles great, until it goes to
>> closed loop mode. When this happens, the ECM starts leaning out the
>> AFR (the block learn goes down the minimum, 108 in this case) to the
>> point where it will barely run. Why is the O2 seeing a rich mixture
>> when it appears it is not? I have tried two O2 sensors with the same
>> result. Does it have to do the the cam duration and manifold type?
>> 
>> I have tuned a few vehicles and I have always been able to rely on
>> the O2 sensor ( with the Integrator and BLM numbers) to get them to
>> run right, until now.
>> 
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