First off, I drive a 2000 civic si. The car runs great but the idle is kind of weird. At warmup it idles between 2000 and 2250 rpm. To get this to drop, even after the car is warm, I have to turn it off and restart the car. After the restart, the idle will move from 1250 to 1500. Sometimes it will drop down to 800-1000, but only after a long drive out of town or something like that. I have adjusted the idle screw to get it down, but if I get it to normal, I still have to shut the car off after warm up to get it down. Once I do this, it wants to run fine until a short drive, maybe 15 minutes and the car will drop idle to 500 and want to die. Anyone have any ideas on how to fix this. There is no engine light light so I didnt know if maybe it was the EGR valve or possibly a vacum line. Any ideas would be greatly appreciated.

 

Sounds like a classic case of sticking IACV. (idle air control valve)

I am not familiar with the Si motor though.

Bump

 

im having a similar issue. it idles fine, until i start driving, when i stop at a light, my car tends to dip low into the 500's and wants to die.

i have the same motor...

 

Mine idles fine at around 1250-1500, its really high. I adjusted it on the intake manifold however, and not the idle control valve or whatever. How much do they usally run, and whats the install time on them?

 

Is that a B16A2?

If so it shoudl be the same as my D16y8 as far as idle operation goes.

There should be an IACV located on the intake manifold. You can take it off and use carb cleaner to clean it out.

then ensure you have the base idle set correctly (this is where I made my mistake)
1. warm up engine untill the fan comes on
2. connect a tach (my inside tach was off)
3. disconnect the IAC vavle connecter and the EVAP purge control solenoid.
4. if the engine stalls restart and try to stabilze the rpm.
5. check idling in no load conditions: headlights, blower fan, radiator fan, and AC are not on.
Idle shoudl be 450+ or - 50 RPM

Turn off the car. Reconnect everything. Then disconnect the neg batt terminal for a few seconds.

Start the car and ilde engine with no load for one min then check the idle speed.
should be 700 + or - 50rpm

if the idle speed increases to 810 + or - 50rpm the EVAP system is purging the can ister. to sto it raise the engine speed to 1000rpm with the throttle then slowly release it.

idle the engine for a min with the headlights on low. idle should be 750 + or - 50 rpm.

then turn the lights off. Idle the engine for a min with the fan switch on hi and ac on . 810 + or - 50rpm.

if its not even close, there are more steps.

IACV is like $200 from a dealer. its a simple device that can be cleaned. If you have over 100k miles on the engine it will be pretty dirty is my guess. There are multiple topics on the forum about cleaning the IACV.

If the base idle is off, it would cause problems with the IACV. There are also numerous sensors that go into the ECU that could be sending false signals. If the above doesn't help I can send you some more info.

 

Thanks, I will try to clean it all out sometime this week, and I will let you know what happens. Thanks for info on this.