idle speed jumps up and down

Hey folks,

I own a 87 accord LXI with about 260k miles on it. Im having a problem trying to figure out what would be causing my idle to jump up and down when in park. When i start the car the idle is sky high at about 2k rpm, then jumps down to under 1k when in gear. I turned down the idle a month ago, but now its back up sky high again. Drive the car for a bit, stick it in park and the idle jumps up and down, up and down.

Ive checked the vac lines as good as i can for leaks and havent found anything. I do have a defective egr valve atm, just need to replace it. It really got worse with the idle jumping up and down after i did a small tune up (plugs, wires, air cleaner, ect) Now it seems to do it when im in drive and let off the gas pedal as well.


Any ideas where to start on getting this solved? Car runs great, but this idle problem is driving my crazy.


Thanks for the help folks!!

vacum leak...THATS the only time it well do that or you IAC is bad....one or the other....to go out and do a quick check get a can of brake clean spary the vac lines if you hear the motor rev up theres your prob....

""When i start the car the idle is sky high at about 2k rpm, then jumps down to under 1k when in gear. ""

you mean when it's cold just started or all the time?
all the time=problem
cars cooler than operating temp= normal. helps to warm it up,thats not high 3k is high
probably a vac leak or iacv like said

Ever figure this out?? I am having a similar issue.

My car did that before but i took off the iac off took it apart and tightend the valve on the inside.

To start off get a 10 socket with socket wrench go to the back of the intake and there will be 3 bolts holding it together.

Next when u losen the bolts get a phillips screw driver and remove the top screw.

there will be two coolent lines connected to it on the bottom just remove those with some pliers.

while the iac is completely off remove the cap off the top of it and get a flat head and u will see that there is a black circular thing in there and with the flat head tighten the valve with the indentations are be sure not to strip it thow because it is plastic

while its off it would be nice to clean it as well could help some more.

after u done tightening put it all back together how u took it off.
hope this helps

thanks I will see if I can find that. kind of funny I plugged the two vacuum lines to the sensor on the distributer and the idle problem went away... LOL

You fixed the vacuum leak so it went away.