Slightly high idle

Hello, Honda's are notorious for fast idle problems. What's going on is the fast idle thermo valve is not closing all the way. It's coolant controlled and located near the throttle plates. It will have 1 or 2 coolant hoses going to it. There is a cover with 2 screws that you can open and adjust the valve. You can even take it off and see if it's hanging open. I've seen most of them are adjustable for some reason. It should look something like this. I would check that first unless you have a vacuum leak. But start with checking this valve that it's not clogged up coolant passages or adjusted it's way out.

I'll have time to do take off that part day after tomorrow, and I'll be checking for any vacuum leaks again. If the problem is fixed after I'll post an update.

Thanks for the info as well.

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Okay, so I've taken off and cleaned the part referenced and reconnected it. I thought I'd take the throttle body off as well to make sure the plate was free of debris.

Now that it's all back on, when I start the car it idles rough at 2100 rpm and has a very loud and very high pitched whine. No idea what I've done or could have caused this.

All hoses are connected properly, as well as wires too.

Well now that the problem is worse. I'd say you're in the right direction. is the coolant system full and bled properly? Since this is a thermal expansion valve, it functions off of coolant temperature. Raising the rpm's while the car is cold and lowering rpm's while warm. Either that valve is bad and sticking open now, or you may be low on coolant. The whining noise is air flow into the throttle body. While the car is cold (in the morning) remove the radiator cap and run the car, let the thermostat open and keep filling it with coolant. This way you bleed all the air out of the coolant system. The high idle thermo valve should be closed when the car warms up as well, this closes off the air port thus reducing the idle.

The coolant is full and bled already. And it's not a normal whine, it's very, very loud and high pitched. I can here it with hood, and both doors closed and it happens as soon as the engine is running.

As far as I can tell, maybe my throttle body gasket is bad, but I'm really worried to even start the car now because of the extremely high idle.

If you removed the throttle body, make sure the gasket for it isn't leaking, this will be a vacuum leak causing high idle also. As for the noise, if it's a bearing, such as the alternator or water pump, then identifying where the noise is coming from is next. You can use a screwdriver to identify where certain noises are coming from. Or a stethoscope, is how a bad bearing would be found. I don't think it has anything to do with the coolant system unless it's the water pump. But they don't usually make whining noises, usually a grinding noise. Can you make a video of the car running so we can hear the noise?

I should have added this previously; remove the alternator drive belt and see if the noise disappears, this will limit it down to just a few components.

Here's a video of the sound I'm trying to explain. Friend who recorded it stated it sounded like it was near my intake manifold.

Also as I said before, when it's running the idle is very high at 2,100 rpm's but does fluctuate up or down. However it flutters at that rpm by about 25 rpm's or so.

That is a crazy sound, so this sound started when you removed the fast idle valve? I would remove it again and see if it's stuck in one position. If the noise started there, it must be related. Although I've never heard one make that noise. Does that fast idle valve have any electrical connections? If so try unplugging it. That sound is of electronic in nature, but the high idle was caused by you removing the throttle body, the gasket should be replaced and torqued to spec. There is a vacuum leak around the throttle plates. Get the idle to come down first and see if the noise continues. Did you pull the valve apart when you had it off the car?

Replaced the throttle body gasket, as it was broken in three places. And the idle is fine and no vacuum leaks.

Car seems to be all good now.

Good deal. Congrats.