Roger Bowman wrote:
>
> Greetings:
>
> I am tracking down a warm start/drivability problem on an '89 syncro westie.
> After the first start of the day, each following start will light off like
> normal, and then settle into an uneasy idle, around 500-600 rpm indicated
> (as opposed to 1100-1200 indicated normally), with no power.  There is no
> power to accelerate, and the motor will not rev even with wide open
> throttle.  The motor will usually stall, but if it does not, after 10-30
> seconds of poor idle/no power, the motor will surge into normal idle and
> power.
>
> Without fail, turning the motor off and restarting (either by compression or
> starter) corrects the problem immeaditely.  I am suspecting Oxygen sensor...
>
> Recent work:  New Temp II sensor, new fuel filter.  Digifant box replaced
> with rebuilt Bosch unit.
>
> Diagnostic Info:  Using my new Fluke 87...
>
> Looking at the Oxygen Sensor:  Engine fully warmed.
>
> - Connected to Harness/Digifant:
> I can see the crossovers; voltage ranges from zero/little negative
> (-.05v-0.0v) to over .9 volts, but the voltage seems to spend most of its
> time in the lower range.  I frequently was able to see the digits resolve in
> the lower range (around 0.0v), with a crossover about once every 1.5
> seconds.  The sensor spent a very short time at the higher voltage, and then
> returned to the lower voltage.  This was pretty consistent; lotsa time at
> low/zero volts, short spike to higher voltage, quick return to lower
> voltage.  Average voltage indicated by meter:  .3v or so.
>
> - Disconnected from Harness/Digifant:
> Digifant side:  about .38 volts
> Sensor side:  camped out at close to zero.  Poor running; replicates
> original problem
>      - Pulling the idle stab hose caused the o2 sensor output to soar to
> 0.9V and idle to smooth.
>      - Pulling the vac hose from the FI pressure regulator and plugging it
> did not show any change.
>
> So:  I'm thinking sensor...and my thoughts cost about $150 or so.
>
> So I pull the sensor and do the bench test thing; find about 3.5 ohms across
> the heating element connection, and when heated with a propane torch, the
> voltage output climbs from 0.0V to 0.9 volts, and falls quickly (within a
> second) when the flame is removed.
>
> Sure would like to confirm a bad sensor before spending all that money; but
> frankly, I'm still not sure it is the Oxygen sensor at all.  I expected more
> crossovers then just one every 1.5 seconds, and I would have expected the
> average value to be close to "Stoich" - which I thought was .45v from the
> sensor.
>
> Any help is appreciated...in advance.
>
> Roger Bowman - bowmanrp@ earthlink.net
> Live Smart.  Think for Yourself.  Transform the Future
Roger
the oxy sensor does not kick in if the throttle switch is not working
properly
Bob