Getting closer to solving rich running (long)

Brandon Rogers brogers at
Mon Feb 18 10:16:42 PST 2008

Guys - 
So this weekend I did some more checking.  As a quick reminder the car
has a very rich exhaust at idle - I _think_ it is fine under load.  The
car did pass Colorado's rolling road emissions - which makes this more
perplexing.  Car has been "rich" (according to my nose and my stinky
clothes after driving it) for a few years....
Ok so here's that info.
Drove the car for a while - fully up to temp - pulled into garage - rich
exhaust stinking up the place - 
engaged ProDiag.  No codes - but pulled up the MBlocks:
1.  Idle Stabilizer Characteristic Control Curve reads 57 (spec is
2.  O2 Adaptation reads 174 (spec is 115-141)
Shut down.
Wait a good hour - pull the two "motor" fuses for about 30 seconds (to
clear adaptations), turn to "on" for 20 seconds, then start.  Let run
for a few minutes but no driving - O2 Sensor Control stays at 128 for
about 2 minutes then after a few minutes:
1.  O2 Sensor Control occasionally climbed as high as 144 (spec is
123-133) then would go back down 
2.  O2 Adaptation goes as high as 142+/- but generally stays in spec -
although on the high end
Last night I pulled the fuses again to make sure I had pulled them long
enough to re-set the adaptation tables.  Did not start car tho.
This AM drove car  - ended up bringing it back home as a nice boost leak
reared its head about 5 minutes from home - but I still hooked up the
ProDiag - NO codes - and on Mblocks:
1. Idle stabilizer in spec - 
2.  O2 adaptation at 142 - just out of spec (115-141) - this may not be
reliable due to leak - but that was only audible at 10 psi+ - so??
Maybe being on the high end of spec it runs rich enough to smell but
still pass Emissions?????????
As for 02 Sensors - - I've used 2 - one of which was a new universal I
spliced into the old harness - and I _think_ the other was a new OE with
connectors.  I could never tell a difference between the two.  
Big question is why is O2 sensor adaptation out of spec?  Bad O2 sensor
(both sensors????)?  Bad something else?  I did try a bone stock ECU and
it seemed to be no different according to my nose - however I did not
pull the MBlocks with it.  

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