Today it's a lot warmer outside, about 44 °F; somewhat more pleasant.
I looked for C144, and found it buried underneath the washer reservoir.
It's a big fat three-pin plastic barrel connector, and the brittle
alignment ears finished breaking off as I played with it. With the
ears missing it can be connected wrong if you're not careful, so I
aligned to the sites of the missing ears and used a Sharpie to mark an
arrow on the barrel that matches one molded into the plug, which should
help. I measured the switch continuity, and found that both WOT and
Idle settings worked correctly. On the engine side the Common and Idle
pins were grounded, as they should be. (One hard ground, one grounded
by the cold-oil sensor.) The resistance to ground of the Idle pin was
23 kΩ, for whatever that's worth.
I rigged a wire from Pin 3 of the engine diagnostic connector into the
passenger compartment so that I can watch the lambda valve duty cycle
as I drive. (This is the BR/GN wire [ground switched] from the valve,
not the BK/RD/WT [positive feed from the fuel pump relay].) I put the
Fluke 87 in the car, as it has a backlight.
On the way to work the Fluke 87 said 70% during warmup. While driving
it was 65–82%, mostly hovered around 70–75%. Idling was 75–79%, I saw
it get to 85% at the end. Idle RPM was lower, down around where it
ought to be. This is pretty rare on this car, in my experience so far.
I wonder if messing with the WOT/Idle switch connector affected this?
On the way home I again saw high duty cycles. (Assuming that these are
to be measured against ground and not across the valve, which would
invert these numbers. [i.e. Wednesday's numbers.]) I checked the other
vital statistics, and the RMS voltage (referenced to ground) was around
6.5–7.5 V, probably OK, but the frequency was very suspect: usually
around 4,400 Hz, but ranging from 2,500–5,500 Hz! Some of my reading
indicates that the 70 Hz range is more what it ought to be. I
definitely think that it's time to haul that engine computer out of
there and have a look at it.
-- Jim
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