Idle air problem, 99 civic

Hi everybody, I have a 99 Civic EX, and I have a little problem with it that I wanted to get other inputs on. Here is the full description of what’s going on.

My check engine light is on and I get the P0505 code from the diagnostic tool, which if I am right, is an idle air control problem. If rev up to about 1,500rpms they starts to fluctuate up and down. If I continue to rev higher it normalizes until I get to about 3,500rpms, at which point it starts to fluctuate again. When this happens as I’m driving it will just pull or bog a little when I shift gears.

What is weird about it is that if I reset the code it will run fine for a day or two until the light comes on again. However, sometimes even when the check engine light is on it runs fine.

I did do some research here on the forum and looked through some posts and it led me to the idle air control valve, cleaning that didn’t do anything. I also read somewhere that you can test the valve simply by unplugging it while it is on and it does seem to be on.

Has anyone had a similar problem? Thanks in advance, all responses are appreciated very much.


PS: Sorry for writing so much, it is just out of concern for my car.:eek:

I cleaned my ports inside the throttle body too. because air passes through there as well. also how is your pcv valve .I changed mine and the idle fluctuating stopped .

I had same problem. Pull back the rubber around wires going to idle air control and the wires are probably rotted away like mine. I still am having all kinds of other electrical problems I have not figured out.