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Hello all,
I just finished a head gasket job on my buddies 2001 Civic EX. The only issue i've had with it now is the idle is really, really weird. The IACV seems to run clean as well as the TB. It idles at a steady 1400-1500 in park but around 1000 in drive, at warm running temp.

I bled most of the air out of the coolant and checked all the hoses for leaks and wires being unplugged. Today I decided to run the car without the air cleaner assembly on and go figure it runs perfectly. ~600 rpm in park, ~600 rpm in drive. The second I put the assembly back on it runs back to 1400-1500. Yes, I have reset the idle computer. Yes, I tried running it without the IAT sensor.

Now what?

 
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Okay so I forgot to mention that at operating temp the intake does sound like a vacuum with the air box off. From what I have read this is from the FITV not closing at idle, but I can't find anything about a FITV in the 7th gens. Do they have them? I have a Honda Service Manual and still can't find anything about it.