My 98 honda civic lx (automatic) idles high around 2000rpm when the engine is cold and when is hot idle goes up and down. I recently changed distributor, distributor cap and rotor. No engine light. Any idea what it could be? Thanks

 

look to see if you have a iacv on the back of your intake maifold, if so then it needs cleaning,
http://www.team-integra.net/sections...ArticleID=1174

 

It could also be the Oxygen sensor.

 

oxygen sensor wont make your car idle up and down, and also if it was bad it would throw a cel, it can be the iacv or the tps

 

thanks for your help 94civichatchback! i cleaned the iacv as you told me, but it didnt chance anything idle still goes up and down. I noticed when the a/c is running, idle stays at 2000rpm, and it doesnt go up and down. Any other suggestion?

 

its not overheating is it?
when i changed the radiator it did this for a bit till i kept adding more radiator fluid as it went down. then i let it ran and it went back to the normal idleing

 

is not overheating! there's plenty of coolant on the radiator and reservor!

 

Does anyone think it could be the throttle position sensor? Just a guess.

 

One more question. Is your timing correct? That might cause it to go up and down due to the computer trying to adjust for it.

 

bleed your coolant system and get the air bubbles out,

unplug your iacv while the car is running does it make a difference?
if yes then its ok, if no then its bad and will need replaced.
the only other thing that causes idle to go up and down would be your tps sensor,
you can either buy a new throttle body and swap it out, or get a dremel and make slots into the screws and unscrew it with a flat head screw driver and swap out the tps sensor.