Idle hunting issues
 

Ok so i got a 1995 Honda civic ex, from the time I bought it the idle has hunted from 1,000 rpms up to 1,500 rpms, then drops and continues doing this. I tried looking online on this forum and Honda-tech and have found the iacv could be the problem. So to do a little test I turned off the car and unplugged the electrical connection. The car now idled fine but the CEL came on. So I turned the car off and plugged it back in, now my idle hunting was back, the other suggestion was my MAP sensor, turned the car off, unplugged, turned on and it’s also fixed. But again I get a CEL on. So reading more a few people said remove the IACV and clean. So I took it off cleaned it. Refilled coolant started the car. Idle went steady and no CEL. I was pleased. After driving around maybe 10 miles my hunting was back, every once in a while it sat steady but 7/10 stops it hunted. Also if it was steady it would sometimes be at 1000, but sometimes it said 500 or so, which is way too low. I have not read anything about stuff like this so I posted, I guess I feel these are my options.

1.) Re-clean the IACV because maybe I didn’t do it good enough (I used a few fills of carb cleaner)

2.) MAP sensor bad?

3.) New IACV for 167.99 worth it?

Additional info: car has aftermarket intake from previous owner? does this affect?

Thanks guys!

bump cause i'm still having the issue, I have been busy doing other things to the car, anyone have an idea with this? do i just start throwing parts at it or is there something easy i'm missing? Thanks.

As it slows down when you unplug the IACV, this means the ECU is commanding a higher idle, which usually results from bad readings from the ECT sensor. The ECU is programmed to run a fast idle until it detects via the ECT that the engine is warmed up. If the thermostat is stuck open, the engine will not warm up. The ECT will also not read properly if there is an air bubble in the cooling system. If the radiator is staying completely full and the engine does run at normal temperature, the sensor itself could be bad.

Okay i'm sorry, so here is some more questions... so I just got the car a few weeks ago. the idle hunting stops when I unplug the IACV or the MAP sensor. there was only once instance where the idle went low, and both the IACV and MAP sensor were plugged in. So maybe Ill just say that was an unrelated issue or a mishap that wont happen again. I have not driven the car in a few weeks now so i do not know if the idle will get low, I do start it up and let it run for a bit every day. I let it heat up till the cooling fan kicks in, then a few more minutes. And there is a idle hunting even when the fan is spinning (which means the car is warm right?) so i guess is there a test for a coolant bubble, or thermo stuck open? If there is any other info that would help just ask, i just want the car to idle smoothly.

With the engine cold, take the cap off and confirm the radiator is completely full. Does the temperature gauge come up to about halfway and stop there?

yes, the radiator is full. And the temp gauge would display just under half. does this mean there is no bubble, i guess what i thought you were saying was there could be a bubble "stuck" somewhere. Is this not true?

brakes applied during erratic idle? my rex did the same thing when my brake booster gave out. small chance, but a vacuum leak there could be an issue.

i'm having the same issue haha

well I decided since there was some oil leaking (what honda doesnt) and it burns a bit also. so I did a compression test. cylinders were as follows starting from distributor to the right.

#1 - 180

#2 - 180

#3 - 180

#4 - 93

so basically I'm screwed =(