At 09:35 PM 10/24/00 EDT, you wrote:
>Get a '95 since the OBD II systems started in '96. The '95 doesn't have a
>sensor after the cat and so the upgrades you do will not be counteracted by
>the computer. JOHN '95 318
The aft 02 sensor only monitors the condition of the cat on 96+'s.
The forward O2 sensor sends a signal to the pcm letting the pcm know how
much oxygen
is in the exhaust gases. While in closed loop conditions, the pcm uses
this signal
in combination with signals from other sensors (e.g. map, tps, coolant
temp., etc)
to make the necessary adjustments to the pulsewidths of the injectors to
arrive at
a stoich mixture. Since this never happens in closed loop, the mixture is
always
bouncing back and forth between varying degrees of lean to rich. In open
loop,
the signal from the O2 sensor is ignored by the pcm, but the pcm still uses
signals
from the other sensors to, find from preset tables of timing and fuel mixture,
which spec.'s to use.
On the 96+'s (OBD-II), the absence of an aft O2 sensor is supposed to but does
not always (apparently) trigger the MIL lamp in the dash. Also, I have never
heard of the computer going into limp mode due to the absence of the aft O2
sensor.
Hope this helps.
Bob
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:56:23 EDT