So I know this topic has been covered 100 times before but I cant find exactly what I am looking for. So my Civic idles at about 1500 which is too high. then it idle hunts from ill say 1400-1600. the tach does not move much but you can hear the difference.

so like everyone else I cleaned my IACV which did nothing. So i unplugged it to see if that would do anything. It didnt. I unplugged my Air Sensor thing ( i think a mass air flow sensor... i dont know its on the throttle body and is not the TPS) so when i unplugged that the idle went way down. So here are my guesses why the idle is high and surging.

1. there is a coolant temp sensor right by the upper radiator hose on the head of the engine. that plug is broken so there are no wires to the sensor. (im guessing that is my high idle since the engine thinks its like -40 degrees)

2. My iacv is broken? cause i would think unplugging it would cause the car to die or idle low or something and it does not change at all, so my guess would be its broken.

so all in all. Is it even bad to have a surging idle, I hardly ever drive the car anyway. and there is a sensor on the thermostat that is the same as the one on the coolant temp sensor. can i steal the one from the thermostat and put splice it onto the wires from the coolant temp sensor?

 

No the sensors are different. You have to have a working ECT (under the distributor) to idle properly. Also if the ECU never sees the engine warm up it will not go into closed loop air fuel control, leading to wasted gas and unnecessary pollution. So replace that sensor plug and get it working right.

Again the one on the thermostat is different, it is an on-off switch for the fan not a proportional sensor.

 

Don't forget the Fast Idle Throtle Valve (FITV). It's located on the throttle body as well. I had this same problem. Replaced the IACV, no change. Replaced the FITV and it's was like new again.