"djathens" <djathens2@yahoo.com> wrote
>I placed an order for the OEM sensor, and downloaded the
>PDF for
> checking the codes. How do I go about purging the cooling
> system of
> air?

A factory service manual for your 88 CRX is free online at
http://www.honda.co.uk/car/owner/workshop.html . See the
procedure for purging (= bleeding) under Engine, Radiator.

> On a side note, does 43-44mpg sound about right for an '88
> w/175k?

fueleconomy.gov reports that the 1988 CRX HF should get at
least 45 mpg in the city and at least 53 mpg highway. That
might be worth nothing. There are some online CRX groups
that you might ask. The Usenet archives (groups.googling for
88 CRX mpg) turns up a wide range, with yours appearing to
be about in the middle.

My 91 Civic has 176k miles on it. Fueleconomy.gov reports
31/35 city/highway. Yet it averages about 40 mpg year-round.
From online reports of other c. 91 Civic owners, that's
pretty usual for a properly maintained one.

Your engine has the same displacement as mine (1.5 L) but
yours is MPFI (mine is DPFI) and 8-valve SOHC (mine is 16).
Also, I suppose your CRX is notably lighter in weight.

Some fuel economy-oriented maintenance tips:
http://home.earthlink.net/~honda.lioness/id11.html

If the car has never had its PCV valve replaced, I'd do
that, first. I replaced my 91 Civic's at 138k miles, and
this made a huge difference in gas mileage, like 10% or so.
The valve was badly fouled with waxy buildup.