mattkins91

I have a 99 civic ex and the idle sometimes gets really low like 300-400rpms. what could be causing that?

slow96lude

IACV try cleaning it out

mattkins91

Can you tell me where i can locate that...its on the throttle body right?

hondamark35

not to be a dick.. but the idle may need to be adjusted.

along with that, you may want to clean the IACV (idle motor) and make sure it's not binding up internally.

take a look at the ignition system components- cap, rotor, wires, plugs and replace if worn. this will help the running overall including idle.

hondamark35

if it's an automatic, it's on the throttle body. if it's a manual, it's on the back side of the plenum near the firewall.

mattkins91

alright thanks i also have a cell for a bad 02 sensor and ive replaced both of them and the light is still on idk what to do

slow96lude

good said mark. how long has it been since it has had a tune up? and yes the IACV is on the backside of your intake mani. Take it off and clean it all up the run 12v across the plug and make sure the valve moves freely. The only thing about adjusting the idle screw to up the idle is the fact that he said it only does it so often

mattkins91

alright ill try that and also my car seems to run great sometimes and other times it seems slow as crap

slow96lude

reset the CEL at autozone

mattkins91

i dont think they will do that cause i was at autozone one day and a guy was trying to get them to do that and they wouldnt do it

slow96lude

Then go somewhere else all they have to do is hook up the obd2 scantool and erase the code. They did it for me the other day after I hade to replace both o2 in my prelude

mattkins91

yeah i guess ill give it a try since autozone is just down the street

slow96lude

it may just be the o2 sensor throwing the ecu into limp mode too. that may clear everything up

mattkins91

what do you mean limp mode

slow96lude

ecu's will go into limp home mode/ lowing the rev limit adding fuel and retarding timing so you dont destroy your engine when something goes wrong. I.E. the o2 sensors

mattkins91

so to fix that i need to get the cel cleared?

slow96lude

yep and hope thats the only one showing and it hasnt stored any more. hopefully it clears I have heard of people replacing the o2 sensors and it still not clearing

mattkins91

so with the me still having the cell is my car running like i havent replaced the sensor or is it running the way it should

slow96lude

its running like you havent changed the sensor. It may be running in open loop

mattkins91

ok so that explains my bad mpg and kinda boggy sometimes

hondamark35

you can clear the CEL yourself by either pulling the 7.5 "backup" fuse under the hood for 10 sec. or pulling the neg. bat. cable loose for 10 sec. both will reset the ECU and clear any stored codes.

mattkins91

Ive done the battery trick and it didnt work

hondamark35

you disconnected the battery, reconnected and then turned the key on and you still had a code stored? or did you start the car and then have a code?

mattkins91

i disconnected the battery and then reconnected the battery and turned my car on and i still had a code