idle is racing when out of gear

the idle is fluctuating extremely high and low whenever i take it out of gear , slow down for a stop. idle goes up and down, in a steady rythm, but sounds like the engine is going to redline if i continue to drive it. noticed it getting worse over the course of a week. it drives but it sounds like the engine is going to blow. any suggestions greatly appreciated. thanks

If your idle is fluctuating, it's more than likely a vaccum leak in one of the hoses on your intake manifold. Spray the hoses with water and see what happens. If you detect an air leak, tape it temporarily and see if that helps. If it does, then replace that hose.

I have been reading this forum quite often as i am getting ready to do a B16a engine swap into my 1991 Civic DX.....a little off topic? Yes

Last week i began to have the same problems as 88civicmc.

Interesting facts about mine....
-Only happens when the engine is warm
-Installed a Tachometer 2 days before the idle went screwy
-Gas pedal sticks...this is an interesting one. When the engine warms up, the gas pedal sticks, causing the idle engine to rev up to 3500rpm. The erratic idling usually goes somewhere from 1000rpm-2500rpm within a two second range. Here's the kicker...Fascinatingly (sarcastic), the sticky gas pedal can be cured by lifting up on the pedal. More fascinating is that the erratic idling can also be cured by pulling up on the gas pedal.
-Car idles (when warm) at 800rpm. Isn't a clean idle, usually a little rough. Been meaning to change the idle speed, but haven't found time.

I am new to cars, but for me, this just seems kind of weird. Is the strange idling in relation to the sticky gas pedal? :uhoh:

Yeah, obviously if your pedal sticks down the engine is going to rev...Also, idle problems can be caused by the EACV...thats the thing on the back of the Intake Manifold with two coolant lines runnin into it, it controls warm idle...

if the eacv is bad your idle will only jump like 500-1000 rpm. sound like you have a vacuum leak on the port that has that rod coming off it on the TB.

You guys always have great input :grinyes: ...the thing that confused me was that pulling up on the gas pedal fixed the high idle RPMs, AND it fixed the idle fluctuation.

The high idle rpms i can understand, but pulling up on the gas pedal to fix idle fluctuation? Doesn't make sense to a rookie...


I understand this is all pretty basic stuff to fix, and chances are through trial and error i'll figure it out, i just have to wait for another sunny day <sigh>

Yeah vaccum leak, but that sounds like a big one....The only way I could manage to get my car to fluctuate like that as when I pulled the Eacv off! the hole in the manifold is pretty damn big, that got to flux up to about 4k then back down..But that was a good point, if the diaphragm on the TB has a hole and you lift up on the pedal it could close the hole and stop the flux.

Maybe your throttle cable is kinked. See if there is enough slack and if there is maybe spray some wd-40 on the throttle mechanism.