I got a 92 Civic a while back. There's some sort of idle issue with it. When I first start it, it idles really high and slowly goes down, but when the rmps get to a certain point, it starts idling up and down until the engine gets warm. I'll try to post a video of it in a while so you guys can understand what I'm talking about. Also the car has high mileage and has a cold air intake. I was thinking it may have something to do with the cold air intake.

 

Most likely has to do with the fast idle thermal valve, if it only does it on cold starts.

 

Get a video for us, but the FITV is located right under the throttle body, it has a coolant line hooked to it and is roughly the size of a couple D batteries lined end to end, and it's bolted flush to the underside of the throttle body. It is responsible for keeping the RPM up higher when the engine is cold.

 

This could be multitude of problems.

Could be a vacuum leak.
Your IACV.
TPS sensor.
Or you could be having a misfire which was my case when I had surging idle. My ecu was fried.

Most common one is your Idle air control valve or your throttle position sensor.

 

He said the problem goes away upon warmup. Due to that I am 90% certain it is related to the FITV and none of these other things.

 

My civics idle surge use to calm itself upon warming as well and it still was my ecu so you never know I guess..

 

I suppose, but ECUs are damn near eternal, and these generation civics are notorious for wearing down their FITVs over time. In other words, between the FITV and ECU its 10x more likely to be the fast idle thermal valve.

OP if you need a picture of it actually in the engine bay I can provide one but the info above should be enough to find it yourself

 

Sorry man. Keep forgetting to get a video. I'll try tomorrow though. I should be able to get to is easily with it being on the bottom of the throttle body. Any idea the cost of the FITV?

 

Check the FITV by taking the intake pipe off so you can see the holes in the side of the throttle body before the throttle plate. Start engine and cover the holes with your finger to see which are sucking air. The bottom one leads to the FITV and should not be flowing any air except when the engine is very cold.

If you don't have extremely cold weather you really don't need the FITV and a lot of people will blank them off (fabricate a custom gasket that doesn't let air through) rather than replace.

 

Can't find it on rock auto, so you'll probably have to get it at a parts store, so maybe a couple hundred

 

Actually i can't find it on a parts store website either. Try cleaning your existing one with brake cleaner, and possibly look into a junk yard.