Just a little caveat: Pinpointing the source of a problem
even with the car right in front of a technician often isn't
easy. A shotgun approach is often necessary. That doesn't
mean people are going to have you rebuild your engine, one
bolt at a time, or anything. It means one can probably
narrow the problem pretty quickly IF the poster is willing
to assist in some troubleshooting and, quite possibly, going
down the wrong path. One has to cover a lot of bases when
diagnosing. Sometimes one nails it with the first base
covered. Sometimes not.

Can you explain in more detail what is happening? Do you
mean that, with the engine running but the car sitting at a
stoplight, and long after warmup, it revs high?

Is fuel mileage poor in general? Does the car seem to run
rough in general?

Have you done any maintenance on the car recently? Is the
car maintained per the maintenance schedule, and using OEM
parts?

Once you respond to some of these, we can talk about purging
the coolant system (costs very little and may be the
problem); checking the idle setting; checking for vacuum
leaks; checking the idle air control valve; replacing the
oxygen sensor.

A wonderful, free online manual for your 1997 Civic that
does have a troubleshooting procedure in it for idle
problems is linked at
http://www.honda.co.uk/car/owner/workshop.html . Maybe start
reading it, starting at the "Fuel Emissions" section where
idle control and troubleshooting is discussed. Keep checking
back.

Big air leak somewhere. Computer is trying to compensate for extra air.

IAC may be stuck, or a hose is disconnected.

Any work done to the car recently? Collisions?

With the car fully warma nd the idle cycling, take off the air pipe to the
throttle body. Find the IAC port and cover it with your finger. Does the
idle drop?

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Make sure the rad is full to the top, and fill the reservoir to the MAX
mark. Drive the car and check it next morning before starting. If it's
'sipped' some of the coolant (no tap water allowed) top it up near MAX
again and repeat next morning. Idle may cure itself. The temp sensors in
the cooling system are 'full emersion' style, and if they aren't under
coolant, the computer goes crazy trying to compensate for bogus input.

'Curly'