Hey i jsut wanted to know in a 97 civic, how is the idle speed controlled, off a sensor on the crank? Or an idle motor in the throttle body or other? And how would adjust it? Im not that familar with honda stuff (used to own ford). Thanks.

 

The IACV, (Idle Air Control Valve) and yes, it's on the TB

 

^^^^ only on most autos. if its a 5speed the IAC is on the back of the manifold if its an ex. lx,dx either auto or manual will be on the TB.

 

what are the symptoms of a bad IAC? My idle is weird sometimes, like it will idle between 100-300rpms, and sometimes it's fine and around 800 or so rpms. Could this be the sign of a IAC that is going out?

 

yes, thats why i ask, sometimes (cold/hot) its fine idles around 650ish which it shoudl be, other times, (cold or hot) itll idle at like 2-300, which it deosnt stall but it is much more shakey than at the 600, not a problem but just annoys me.

 

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Honda's are good for funky idle problems... mine sits around 3-400 most of the time.

Typically if your IACV is bad or clogged.... the idle rpm willl jump up and down constantly as if you were pressing the gas and letting go, pressing the gas and letting go, etc...

If it is just idling low sometimes and a little higher other times without the constant up and down then it is probably not the IACV. You can pull it off though and just check the screen to see if it's clogged if you are concerned. It will be on your intake manifold either on the front or rear depending on year and model.

Also keep in mind that your car will idle higher while the motor is cold and trying to warm up... this is normal and is made to do that. i.e. my normal idle is around 3-400 but whne I first start it and the motors cold, it will idle at around 1k until it warms up then it returns to its normal 3-400 range.

 

Sometimes when it's cold out around here, it idles at like 2k rpm's I'm not sure that it's normal cause i've gotten jumpy idles at sometimes aswell, so I need to clean the IACV probably.

 

alrighty i understand the warm/cold idle thing, wells here my situation: my car would idle at whatever b4, but now when it idling ( i think too low) like 300ish, its much shackier, not horrible but you used to never feel any vibration, when i increase the idle ever so slighty with the pedal, its fine and smooth like around 6ish. Here's another wired thing, when its real warm sometimes when the idles low if i have my flashers on, the engine moves faster and slower with the flashing, very little but i notice it, like 50 rpm's so whats up with that, and i was hoping to manually jsut increase the idle slightly, is this possible? Thanks. (sorry for the story)

 

to adjust your idle, there is a flat head screw (not actually a screw) that is on your throttle body and sits just above your intake pipe. It may be sealed so you may just see the circle where it is covered with some sort of sealant. If you have that then just scrape it out to expose the flat head screw.

Turn it counter clockwise to open your throttle a bit more and increase the idle rpm. If you want to start from scratch, turn it clockwise until closed all the way then open it again by turning counter clockwise until it idles where you want it... it's usually about 3 1/2 turns... don't do too much more than that or your idle will jump around when the motor is warm.

You'll of course want to wait until the motor is warm before adjusting the idle.