OK. I had a check engine light on and it was the o2 sensor. The manifold also had a crack in it. Then my idle would go low sometimes. I replaced the manifold and the 02 sensor and I did get my check engine light cleared but there is still a problem. When I start the car it idles fine. But after driving it a little bit it idles really low. When I am in neutral and I hit the gas and let the idle go back down it goes down so low that I have had the car shut off but most of the time it goes as low as 100 or 200 RPMs. What is causing this? There is no check engine light right now but it still idles too low.

 

i think you should check your IAC valve. Also does it do this after it warms up or when the engine is still cold?

 

could be a number of things. But you would want to definitely check your IACV like my man above said. You might also want to look at your Throttle Position Sensor (TPS) and also make sure you dont have any air in your cooling system. Good Luck.

 

It only does it after it warms up. It idles fine at startup. Even if I run the car for awhile and then shut it off and start again. When I just start it it idles fine.

 

Where is the IAC valve located in a 97 civic

 

is it auto or 5 speed?

 

5 speed

 

Is there any way I could clean the valve or test it to make sure that is the problem.

 

Are these hard to clean or easy?

 

I've the exact same problem. Trying to address it currently.

 

here is a link to a great write up on cleaning it...

https://honda-tech.com/zerothread?id=1575913

 

Good write up, but these are 96+ cars. They have an EACV which has a rotary valve inside it.

The EACV is located in front of the throttle body, underneath the air cleaner, kuks24