I agree, I had a cruise control cable stick on my 85 nissan that caused this
problem, made the throttle stick way too far open.

ITEM #1. _check the throttle cable._  it's probably sticking open.  the
engine /cannot/ rev is it's not getting air & gas.

if that's not it, i concur about leaving it on - the rev limiter will
protect it, so see if it corrects with the eacv.  also look for vacuum
leaks.

<snip>

Also, what kind of maintenance has the car had? When were the
cap/plugs/wires and rotor replaced last?

Does the car seem to have poor power all the time, and to start slowly with
lots of cranking?

Please turn quoting back on in your newsreader.

You have an odd problem indeed. This phenomenon could /only/ occur if an
adequate amount of fuel and air were being admitted to the intake, that
amount increasing with the revs, so as to sustain the increase.

I almost think you have a dirty throttle body that is so filthy it's
causing the throttle plate to stick open.

Low coolant results in surging (like with a big air leak), not a steadily
increasing idle that occurs over 4 or 5 seconds.

Questions (please intersperse your answers):

You say it's "recently" been doing this. When is "recently"?

Had the vehicle been subject to heavy rains or driven through deep water?
Had a collision?

What happened to/with the car immediately before it started to rev like
this?

If you were to let it rev, will it eventually reach redline? You have a rev
limiter, so it ought to go no further than abut 6,800 rpm.

Well, RPM goes like 5000 in only 4/5 seconds. I never let it go higher.

I didn't purge the air intake. Do you think that may solve the problem?

How high is the RPM revving?

Did you purge the coolant system of air?

I find it takes at least a half hour of the car sitting at idle before the
fan comes on twice, during the purge process.

If air is in the cooling system, then certain engine control components are
not necessarily being cooled adequately, and erratic revving will occur.
Very common problem which is easily fixed.

Sorry that I didn't make that clear. Mine is 89 Honda Civic (Wagovan).
Recently it's been doing that (High RPM when engine is hot). I thought
radiator flush was the problem as I never done that in the past. Flushed
last week and didn't solve the problem.

Also my car is 5-speed manual (1.5 liter and currently about 150000 miles
on it).

Could you please help.

---------------------

This is not a 'psychic automotive diagnostic service'. Look in the
Yellow Pages for that.

All we know is that it has a key, and that it overheats. It could be a
Honda motorcycle. . . . . Help us out a bit.

'Curly'

When running, no problem. When in neutral (class released), RPM goes
tremendously high. I usually have to turn off the ignition and turn back
on to move on about a feet in STOP signs.

It only happens in Summer and when the engine is already hot (Engine
Temperature is normal though).

Please tell me what shall I fix.