OXS (Frequency valve) duty cycle

[DH5481@aol.com]

I'm trying to read the duty cycle for my '87 5KCSTQ.  With the dwell hooked
up to the test point, all I get is 95% duty cycle - which should correspond
to the rich limit.  Shorting the temp thermoswitches (there are two - not
sure which one) to ground "should" kick it into open loop (simulating a cold
engine) of around 60% - zip...  Disconnecting the O2 sensor and attaching a
1.5V battery to the ECU input "should" drive the duty cycle to the lean limit
(10%) - still no change...  1/2 turn on mixture to lean - no change.
Am I doing something wrong, OR (shudder) could there be an ECU problem?  I'm
going to recheck in the morning cold (45 degrees in Orlando - brrr!) since
the car has much more power when dead cold.  I am reasonably certain the )2
sensor is toast, and plan on replacing that anyway, probably this weekend.
 Symptoms for car are as for a bad O2 sensor.  Poor accel, hesitation when
warm.  MPG 20 ave, 26 highway, 19 in town.

Dave Head
87 5KCSTQ