irratic idle problem 92 prelude si

my 92 honda prelude has an abnormal idle...it will idle at around 1500
rpms when in drive (its automatic) and when i put it in park or
neutral it goes from 1200 to 1800 rpms as if im hitting the gas over
and over again(it pulsates). my check engine light is on...does anyone
know what the problem could be?

 

Low coolant, vacuum leak, bad fast idle valve, bad EACV... etc. etc.
I'd pull the codes and see why the check engine light is on.

 

Not too certain, although I know this is a problem that plagues some Civics;
my brother's included. For some it's related to the IACV, the Idle Air
Control Valve; others have had it corrected by cleaning out the throttle
body (it can get pretty clogged, especially after 13 years). Like someone
said, short the service connector: it's a little blue plug in the center
console area behind the radio, it looks like a phone jack but with 2 holes.
Grab a paperclip, straighten it out into a U, and stick it into both holes.
Now turn your ignition to the accessories on, the position just before
starting the engine - the Check Engine light will blink in a series, just
count how many long and short blinks it gives, for instance 2 long and 3
short is CEL code 23, 6 long and 5 short is code 65. Post again with all
the codes you get, it'll pause a few seconds in between codes if there are
more than one. If you miss one, just turn the ignition off and do it again.

--
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Danny D. Ruiz | How many times do you hear it? It goes
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