4kq bad mileage (still!) (longish)

[Brady Moffatt]

Well,

Thanks to all who gave me advice so far. Here's an update:

Checked the injectors. They flow fine. Recent plugs, wires, cap, rotor, 02
sensor. CO within spec. Cars runs well.

I have a new thermostat (87-92C). The old one was opening too early, but not
by much. The heater is a bit quicker now. That's about it. The temp gauge
still reads low, but the rad fan cycles on and off every now and then, so
presumably the engine is up to temp. The fuel gauge works fine so the
voltage reg in the dash must be fine, and therefore, presumably the temp
gauge is OK.

BUT, my mileage still sucks (17mpg).

Huw, I saw something on your site where you cleaned up the ground contact
(bolt) at the upper rad hose flange. You mentioned that a bad ground could
mess up temp signals (voltage) to the ECU (and the gauge I guess). After you
did that, did your mileage improve a lot? Or was your only problem the
thermostat?

Now, on the flange, there are 2 sensors. Top one is the gauge sender, and
the bottom one is the thermo-time switch, right? According to Bentley, it
and the temp gauge sender don't have separate ground wires, so they go to
ground through the housing, right?I guess cleaning up the flange bolts and
the threads on the sensors might fix my gauge, but that's it.

So, where's the "temp sensor (NTC)" that the Bentley shows on 97.270 track
27? It grounds by wire to the intake manifold? It goes to the ECU. My guess
is that's what I'm looking for for my mileage woes.

HELP!

Thanks,
Brady Moffatt
Montreal, Quebec, Canada
86 4ksq, 280,000km
72 Datsun 240Z, 180,000 miles