My car used to have the infamous fluctuating idle but I replaced the IAC and calibrated the TPS but now I have a constant high idle at 1500rpm. I've been checking for vacuum leaks, getting air out of the coolant, getting a new Throttle Body gasket, and resetting the ECU.
Things to note: My idle speed screw cannot go any lower. When I shift out of Park the idle speed goes down to normal. Also I plugged up the throttle body and the 2 vacuum lines but wasn't able to kill the car completely. Very close but not completely.

When I block this vacuum hose the idle speed goes down.

Check engine light was because I unplugged the IAC

I can hear air from the intake filter. Is that normal?

IAC



I unplug this fuse to reset the ECU, correct?

 

plz

 

To reset the ecu you can simply disconnect the battery for a few seconds. Start there and make sure your check engine light goes away. If not, look into the code. The vacuum hose you pointed out in the first picture should go to the vent in the valve cover. Not sure why that would make the idle go down.
Hearing air rush by at the cold air intake is pretty normal, I think. More annoying than anything if you ask me, if I had a stock intake I’d have put it on.
Lastly, you should have already checked but make sure your throttle cable isn’t pulling on the throttle slightly because that would obviously make it idle high.

 

Why not just block off that hose that makes the idle go down? I cannot tell where it goes but its not going to harm anything

 

Where does that hose in pic #1 go? It suppose to go to the valve cover.

edit: nvm I see the other hose going to the valve cover.

 

The silvery metal hose goes to the valve cover, maybe you're getting them confused? Throttle cable seems fine, I even let it hang totally loose. The stock intake was broken so having this is easier to work on (and sounds cooler) I had an eBay intake earlier so it's hard to believe it's the intake.

 

I feel like that's just masking the issue. I want to do this the right way before doing that instead although that might solve the problem

 

It's possible I didn't get all the air out of the coolant? Or air is not being allowed to escape

 

It looks like the inlet hose for the Air Injection Valve which is mounted on the corner of the intake manifold. The hose coming out of the top of this device connects to a barb in the middle of the top edge of the intake manifold casting between the second and third intake runners. Try blocking that side of the hose instead and see if you get the same result in reducing the idle speed. If so, you likely will need to replace this Air Assist/Injection valve. There is also a possibility that you have a HUGE air bubble in the cooling system, so properly bleeding the cooling system first may solve the idle problem.

 

Do you mean this one?

 

I took my Air Injection Valve out and looked at it. Is the bottom pin supposed to move? Because mine was stuck and wouldn't decompress. I bled the coolant for about 20 minutes but stopped because it was getting late and there were still very very tiny bubbles forming, nothing major though. If I turned the AC on the idle would go way down, but once the AC compressor stopped running it would go back to where it was.

 

Yes, I meant that hose that you highlighted. If pinching that hose near the center of the intake manifold drops the idle, I would replace the Air Injection Valve.

 

Find out why the CEL is on and resolve it.

Make sure all sensors are plugged in correctly. The 2-wire and 3-wire plugs are physically the same so they can be plugged in to the wrong thing. Use the sticky at the top of this forum to check the wire colors.

With a 2 wire IACV an important test is to unplug the IACV and the idle should drop to less than normal.
Idle does not drop -- air leakage. With nothing leaking closing the screw should reach 450 rpm which is the proper setting-- if you don't have a good service tach go for "barely running".
Idle does drop -- ECU is holding idle speed up, likely temperature sensor problem.

 

man...I want a shiny new arm now...

 

I unplugged the IAC when it was running once and my car starting "puffing" like a throbbing idle. I cleared the code which was p0505 and drove around and it hasn't come back yet. Did the idle speed drop? Yes but not the way I expected.
I have a new Air Assist Valve, Temp Sensor and IAC on the way because the IAC I bought was super cheap Amazon type

 

Update: It must have been a bad IAC. The new one seems to work much better. Bleeding the coolant helped too.