So when I did the f22 to f23 intake manifold swap I had to cut a bit of the IACV nipples and put longer coolant hoses in. I notice afterward that I have a delayed idle. It goes from 1000rpm, in neutral, to 750 rather than smoothly dropping down to 750. I accidentally disconnected the coolant line going out of the IACV and into the pipe under the manifold but there was no coolant running through.
Is the coolant system picky with hoses at all? Or is there too much air in the system?
I tried the procedure to get air out of the coolant by letting it run through the top hose from the head to the radiator and squeezing that to release the bubbles but I'm not sure if that was enough. How can I get all the air out of the coolant system and make sure that the IACV is getting an adequate flow of coolant? Or would coolant flow not be the cause of a delayed idle?

 

There is a bleeder valve near the thermostat close by the intake manifold. Losen it and fill the rad with coolant then check bleeder if the fluid flowing out is completely of bubbles then you can tighten it after.

Hope this helps

 

Jack the car up as high as you can in the front end before you bleed it.

 

I did use the bleeder valve too but the iacv coolant line makes me suspect that coolant either isnt flowing through there or that theres air still in there. Problem is that the IACV is higher up than the radiator or bleeder valve

 

the only function the coolant serves running through the throttle body is to warm up the air charge more quickly when the engine is cold. it will have nothing to do with how the idle changes when you put the car in neutral...

 

So do you think that my IACV is defective then? Or could it be something else that is delaying the idle? I dont think anything is getting caught on the TB cable and the throttle plate opens and closes fine. Or could it be that the rush of air going through keeps the plate from closing as quickly at times? I have a 3" intake pipe rather than 2.5". Or that shouldnt make a difference...

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just an afterthought, it could be the angle of the bracket holding the cables and I'm just not noticing it when I'm under the hood rather than behind the wheel. Ill check that out first.

Simple things, simple things, its always the simple things.

 

I compared my data for throttle position and rpm's in the same trip and spots where the rpms go to 1000+/- for a second before dropping have a 9% throttle position indicating that the throttle plate is not open when this is happening. either that or the tps is faulty. but youd see that in my data. Faulty IACV anyone?

 

You may want to check that the coolant passage through the IACV is not clogged. I would suggest NOT to remove the plate with the two lines going into the IACV, because the gasket is a pain to reinstall. Maybe try a small screwdriver or a pipe cleaner.

I know that someone posted about that causing his IACV problems a while back on here.

 

I took the IACV out a while ago and ran water through it, it went through fine so I know its not clogged. And coolant is in there. It just didnt pump out when I knocked it off with the car running.

 

I'm not quite sure exactly what your issue is. If it idles at 750, then it's fine. I don't think that hose it going to have a big gush of pressure in it. The hoses going to the iacv only serve to keep the iacv from freezing up when the car sits during a cold winter night. They don't serve any mechanical function at all.