Do you mean the intake air temperature sensor (a.k.a. TA sensor)?

www.autozone.com has free repair guides for the 93 Civic and indicates it does
have a TA sensor. It's listed under "Emission Controls, Electronic Engine
Controls, PGM-FI system."

My understanding is this a pretty standard sensor on many (all?) cars built in
the last twenty years or so, as emission control requirements became more
demanding.

Also, http://www.hondaautomotiveparts.com/auto/jsp/mws/catdisplay.jsp lists the
TA sensor for  my 91 Civic LX under "Intake Manifold." Probably there for your
93 Civic, too.

It does have an intake air temperature sensor. See page 11-68 in the
manual found at http://www.hondahookup.com/manuals/USDM_92-95_civic.zip
or look at http://www.honda.co.uk/owner/civicmanual/pdf/11-50.pdfc and
http://www.honda.co.uk/owner/civicmanual/pdf/11-3.pdf