FC 45

[Mike Pitts]

That's interesting.  I had a bad O2 on my GN last year 
which caused me to fail the emissions check.  I replaced 
it with a Bosch and with a little tuning, I was able to 
get my emissions down to 6 pmm of HC. Max allowable is 
220 ppm.  Before the sensor change it blew something 
like 330 ppm.

Maybe the Bosch sensors work fine on the older C3 ECMs 
but not the newer P4s ?

-Mike

-----Original Message-----
Matt,
Trash that Bosch O2 sensor...
The Bosch O2 sensors isolate the grounded side of the sensing element from
the shell... AC grounds the low side to the shell... The computer needs the
ground.  Fought this on my 95 lesabre for a week... goes pig rich due to the
floating ground.
A quick test is get the wiring diagram and take the low (grounded) side of
the O2 sensor element and run a wire to the block.
Guarantee the problem will disappear.  Bosch responded to me that they knew
it was a problem, but they weren't going to change manufacturing.