[s-cars] Fuel mixture, boost, throttle position

[Stott Hare]

So in my effort to identify my horrendous fuel mileage under cold
temperatures (normal temps/driving style 21+ mpg - normal driving/temps
below 25*F <19mpg - same crap fuel with ethanol mixed in) and track how
the car is running in general, I integrated an air/fuel meter into my
PRNDL blank spot of my instrument cluster.  I'm running a generic 13913
sensor and have modified the O2 sensor harness to include the Ford
connector for the 13913  (sensor to 13913 junction to remainder of stock
O2 harness to stock O2 junction with the ECU harness).  I don't have the
response time of a wide band sensor, but the 10 segment LED I used goes
2 red bars lean, 2 yellow bars, 2 green bars stoich, 2 yellow bars, then
2 red bars rich.  I've been watching its behavior for a couple weeks
now, and I've noticed it leans out in partial throttle acceleration
situations (anywhere around half throttle or so) such that no display
segments are lit.  Once I've added more throttle (triggering the WOT
switch I assume) mixture comes right back up to one yellow segment above
stoich.

 

Just curious what other people who have/watch air fuel gauges see.  I'm
wondering if this is a common place for the motor to lean out, or if I
have a dead spot in my throttle position sensor which is messing things
up.

 

Other data:

The 2pin white temp sensor at the back of the head for the ECU was just
replaced.

The 4pin brown multi-temp sensor was replaced 75k or so ago - although I
have no apparent problems with it, cluster temp gauge is rock solid
consistent.

Thermostat was replaced with T-belt about 30k ago, and appears to be
functioning well/properly.  Temp gauge is rock solid regardless of what
the car is doing or what the outside temp is.

13913 Oxy sensor was replaced 25k ago or so.

HVAC 2pin blue temp sensor and the notorious plastic housings were
replaced with tbelt about 30k ago.

 

Interested in hearing the thoughts from the collective.

-Stott

95 S6A (280k on the clock)