Ok here goes, I have a B16A in my EG civic and have been having trouble with the idle lately. When cold it will sit at around 3,000 rpm. Once the engine gets kinda warm it bounces from 1,000 to 2,500 and back again. I got a new ECT sensor and when I plug that in (out of the motor) my idle sits at ~3,100 rpm. My question is has anyone had a similiar idle issue and how did you fix it. There is a little test for the fast idle thermo valve in my factory service manual that I was gonna do tomorrow but if it doesn't shed light on the situation I am kinda lost. Besides just starting replacing everything that has to do with the idle. Any suggestions? BTW there is no CEL indicated, so it isn't in the wiring. Any help would be greatly appreciated.

 

I have an obd2 hatch obd1 motor, when using the harness, I pulled the IACV wire out and it fixes me idle surging.

 

so you think it is most likely the IACV?

 

sounded like your ivac is working. check the fast idle thermal valve. there is a write up on how to check and clean it. since that you have a factory manual then you are good to go on how to check it.

 

hard to say... the reason being is on mine for instance, it would just go up and down like your "warm engine" does but all the time. I never had anything over 3k.

I'd clean your thermo valve since thats an easy fix if you have the helms and then shoot from there. Its not your ECT because your arent throwing cel 6.

 

It ended up being the fast idle thermo valve. Thankefully I had a spare sitting around at home.