RE: [alfa] Code 1223 on a 92 Spider Veloce

["Peter Webb" <webb.p@xxxxxxxxxxx>]

> After reading through the manuals, TSBs, and previous discussions
> about 164s
> with the 1223 error code (O2 sensor at limit) and still not coming to a
> complete resolution, I decided to make the post.  So here goes:
>
> Problem:
>
> Intermittent check engine light giving 1223 - O2 sensor at limit.
>  The check
> engine light comes only after operating temp is reached under the
> following
> conditions:  1.  idle for extended periods.  2.  Constant low rpm
> throttle (i.e.
> at cruise) for extended periods.  The check engine light will go out upon
> increased acceleration and/or rpm--downshifting.  Other than the
> light....car
> seems to be running fine with no loss of power.  Idle is smooth
> on startup and
> after warmup.  Acceleration is smooth cold or hot.  I do hear a
> new middle
> muffler exhaust leak that coincides with this problem.
>
> Maintenance from AUG 2003 - new O2 sensor, new soft rubber intake
> air hose.
> Car has been error free for several months.
>
> I have checked for air leaks, water in electrical connections to the O2
> sensor, Throttle Position Sensor, and AFM.
>
> TSB mentioned exhaust leaks.  My question is could a middle
> muffler exhaust
> leak....that is not pouring exhaust out....result in such a
> predicament?  I am
> heading to midas in the morning in any case.  But was wondering
> if anyone has
> had the same problem resulting in a 1223 code.  Finally, if I end
> up removing
> the middle muffler and replace with straight pipe, is the
> motronic limits so
> sensitive that removal of that amount of back pressure will send
> me to check
> engine code hell?

At a guess, your EGT (exhaust gas temps) are too high and frying the O2
sensor.   This can be caused by exhaust leaks (see below) but usually from
running too lean.   Put a VOM on the O2 sensor and see what the readings
are.   You should be bouncing around 0.48v at idle.   If you get no voltage
or constant pegged at 0.8v the O2 sensor is totally dead.   The code is
probably the 0 voltage from the sensor.  You'll need to replace the sensor
no matter what, and a new one will help diagnose this by gauging the EGO.

See if you can get some EGT temps from around the exhaust manifold after
idling for a while.   Better yet, do it at night.  Open the hood and you'll
probably see the manifold glowing.

Why you're running lean is another story.  You'll have to check all the
sensors but I'd put my money on the AFM.  However, an exhaust leak can cause
a pressure drop in the exhaust port and change the way it scavenges making
it run lean.  This was just well covered on the MegaSquirt list when someone
ran at altitude without barometric compensation turned on with the same
result.   The reason; lower barometric pressure caused the exhaust to
scavenge quicker (less back pressure) making it go lean.  Once baro
compensation was turned on, everything was right in the world.

-Peter
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