O2 sensor in muffler?

I'm looking at the Cobalt cat-back system from Moss for my '96. On the same
page they also list a "bung plug" because the system comes with "2 holes,
and 90-95 only needs one".

I thought the O2 sensor was by the outlet of the header. Are there more
south of the catalytic? Does my '96 have 2 down there?

TIA,

miker

miker wrote:
> I'm looking at the Cobalt cat-back system from Moss for my '96. On the same
> page they also list a "bung plug" because the system comes with "2 holes,
> and 90-95 only needs one".
>
> I thought the O2 sensor was by the outlet of the header. Are there more
> south of the catalytic? Does my '96 have 2 down there?
>
> TIA,
>
> miker


I only remember one on my previous 1996 model, pretty sure on that, but
not positive.

There is only one oxygen sensor listed for sale for either 1990-1993
Miatas or 1994-2000 Miatas, so I am guessing that this is correct.

Pat

> > I thought the O2 sensor was by the outlet of the header. Are there more
> > south of the catalytic? Does my '96 have 2 down there?

> I only remember one on my previous 1996 model, pretty sure on that, but
> not positive.

Thanks... Where on the exhaust was it physically located?

miker

According to Rod's Enthusiast's Shop Manual, there is an oxygen sensor
before and after the catalytic converter (a total of two sensors) for the NA
referred to as the front and rear. But later in the Rod's manual as it
details exhaust system removal it says "if your car has a heated oxygen
sensor in the exhaust pipe after the catalytic converter..." which may be a
nod to Miata's in other countries. I think there is one in the cat-back
section that you are looking to replace, certainly not two. You probably
should stick your head under there and have a look. It would be in the pipe
just rear of the cat. The other one is clearly seen in the engine
compartment sticking out of the rear of the header.

"miker" > wrote in message
m...
> I'm looking at the Cobalt cat-back system from Moss for my '96. On the
> same
> page they also list a "bung plug" because the system comes with "2 holes,
> and 90-95 only needs one".
>
> I thought the O2 sensor was by the outlet of the header. Are there more
> south of the catalytic? Does my '96 have 2 down there?
>
> TIA,
>
> miker
>
>
>

> According to Rod's Enthusiast's Shop Manual, there is an oxygen sensor
> before and after the catalytic converter (a total of two sensors) for the
NA
> referred to as the front and rear. But later in the Rod's manual as it
> details exhaust system removal it says "if your car has a heated oxygen
> sensor in the exhaust pipe after the catalytic converter..." which may be
a
> nod to Miata's in other countries. I think there is one in the cat-back
> section that you are looking to replace, certainly not two. You probably
> should stick your head under there and have a look. It would be in the
pipe
> just rear of the cat. The other one is clearly seen in the engine
> compartment sticking out of the rear of the header.

Ok, I see two... one at the base of the header, one between the cat and the
resonator (pointing straight up). Sounds like Rod means these two. But the
Cobalt cat-back comes with two holes, which would be in addition to the
header one... so some Miata's must have three O2 sensors.

Looks rusty - do these sensors usually unscrew easy? Or typical exhaust
trouble and strife?

miker

"miker" > wrote in message
m...
>> According to Rod's Enthusiast's Shop Manual, there is an oxygen sensor
>> before and after the catalytic converter (a total of two sensors) for the
> NA
>> referred to as the front and rear. But later in the Rod's manual as it
>> details exhaust system removal it says "if your car has a heated oxygen
>> sensor in the exhaust pipe after the catalytic converter..." which may be
> a
>> nod to Miata's in other countries. I think there is one in the cat-back
>> section that you are looking to replace, certainly not two. You probably
>> should stick your head under there and have a look. It would be in the
> pipe
>> just rear of the cat. The other one is clearly seen in the engine
>> compartment sticking out of the rear of the header.
>
> Ok, I see two... one at the base of the header, one between the cat and
> the
> resonator (pointing straight up). Sounds like Rod means these two. But the
> Cobalt cat-back comes with two holes, which would be in addition to the
> header one... so some Miata's must have three O2 sensors.
>
> Looks rusty - do these sensors usually unscrew easy? Or typical exhaust
> trouble and strife?
>
> miker

Miatas come only with 2 sensors. The extra hole will be plugged. There may
some difficulty removing the old sensor so make sure to use a socket, not an
adjustable wrench.

"Chas Hurst" > wrote in message
...
>
> "miker" > wrote in message
> m...
>>> According to Rod's Enthusiast's Shop Manual, there is an oxygen sensor
>>> before and after the catalytic converter (a total of two sensors) for
>>> the
>> NA
>>> referred to as the front and rear. But later in the Rod's manual as it
>>> details exhaust system removal it says "if your car has a heated oxygen
>>> sensor in the exhaust pipe after the catalytic converter..." which may
>>> be
>> a
>>> nod to Miata's in other countries. I think there is one in the cat-back
>>> section that you are looking to replace, certainly not two. You
>>> probably
>>> should stick your head under there and have a look. It would be in the
>> pipe
>>> just rear of the cat. The other one is clearly seen in the engine
>>> compartment sticking out of the rear of the header.
>>
>> Ok, I see two... one at the base of the header, one between the cat and
>> the
>> resonator (pointing straight up). Sounds like Rod means these two. But
>> the
>> Cobalt cat-back comes with two holes, which would be in addition to the
>> header one... so some Miata's must have three O2 sensors.
>>
>> Looks rusty - do these sensors usually unscrew easy? Or typical exhaust
>> trouble and strife?
>>
>> miker
>
> Miatas come only with 2 sensors. The extra hole will be plugged. There may
> some difficulty removing the old sensor so make sure to use a socket, not
> an adjustable wrench.
>

Rod's suggest that the sensor is more easily removed when hot, but cautions
about wearing protective gloves to prevent getting burned... and that you
need a new washer to reinstall the sensor. It goes on to warn that the cat
retains heat for a very long time (longer than the rest of the exhaust) and
should be "stone cold" before working on it to prevent from getting burned.

Depends-- OBD1 vs OBD2 US models--96-97(OBD2) was a change over as I
remember.
It may be that late 96 build dates had a sensor added.
The addiitonal bung & plug are so that the exhaust system can be used on a
97 as well.
The aftermarket replacement midpipe (converter & muffler assembly) on my 99
has two bungs, one for the second O2 sensor, and one extra (ahead of the
converter) for a wide band or a dyno sensor. The downpipe has the first O2
sensor.


"miker" > wrote in message
m...
>> > I thought the O2 sensor was by the outlet of the header. Are there more
>> > south of the catalytic? Does my '96 have 2 down there?
>
>> I only remember one on my previous 1996 model, pretty sure on that, but
>> not positive.
>
> Thanks... Where on the exhaust was it physically located?
>
> miker
>
>
>
>