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Old 01-10-2008, 11:08 PM   #1
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Default IAC help needed. please help

hello
i am driving a 01 miata . i built my own turbo kit and am having some idel issues. i am thinking my IAc is bad and causing the issues. I am wondering if there are any members that can let me use their IAC or the whole throttle body just to make sure that it is my problem. maybe some supercharged guys have throttle bodies laying around. If anyone can help me out please let me know or if someone is selling a IAC also let me know.

i never heard it click before and that is why i am thinking it went bad. my idle is fine until the car warms up and i drive if for a while. after about 10min driving comming to a stop the idel drops around 500rpm and car wants to shut down. i checked all the vacuum hoses and i don't see any leacks. Maf is fine i put it in my friends car and works fine on his. what else can it be? i read all the idel threads and followed that adivise but no success.
thanks for the help
-jasko
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Old 01-10-2008, 11:11 PM   #2
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if it was bad the idle would hunt (ie, go high and then low, oscillate back and forth).
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Old 01-10-2008, 11:14 PM   #3
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Is your BOV leaking at idle? What kind are you using?
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Old 01-10-2008, 11:18 PM   #4
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i am using a diverter valve. i checked the hoses from that to the maf and no leaks. i am using a forge diverter valve. my idel does hunt but only slightly . nothing major. maybe 100rpms up and down. mostly when the car is cold.

another thing i can add is that when i stop at a light the idle is high at first like 1500rpm and stays ther for about 3sec than drops to 900.
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Old 01-10-2008, 11:22 PM   #5
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sounds like a leak.
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Old 01-10-2008, 11:29 PM   #6
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man i dont' know where to look any more. is there a way to test for leaks ? i checked the vacuum lines for cracks did not see any. i threw a code once which was the IAC malfunction. the vacuum on my greddy gauge shows -9.6psi when idel jumps to 1500rpm but as the idel drops to 900 it shows -8.6 psi it should of been the other way arround should it not?
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Old 01-10-2008, 11:40 PM   #7
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http://www.dsmtuners.com/forums/arti...your-to4e.html

I made something similar to that. I found parts at home depot and walmart.

Edit: and here's another. http://www.vfaq.com/mods/ICtester.html

Last edited by Bryce; 01-10-2008 at 11:45 PM. Reason: Added another link.
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Old 01-10-2008, 11:50 PM   #8
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It's a common problem among NBs to have a bad idle like that. The most common fix is to take the throttlebody off, clean the IAC valve and throttle body. Including pulling out the idle screw and cleaning the hole in there. You have to get the screw out to clean it right though.
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Old 01-10-2008, 11:52 PM   #9
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great items there i will make one tomorrow to test it out.
keep the recommendations comming i am appreciating every single one of them. thanks again guys
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Old 01-11-2008, 10:57 AM   #10
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ill be up there all weekend, come by and we'll play around some more to find out what it is...
also, anyone know a simple way to revmove the idle skrew if you dont have the tool
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Old 01-11-2008, 01:47 PM   #11
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Loosen the screw. Then use an aircompressor on the backside to blow air through it forcing the screw out.
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Old 01-11-2008, 05:24 PM   #12
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we tryed that last time, didnt work to well but we gave up kinda quickly on the idea, we can try that again...
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Old 01-11-2008, 07:45 PM   #13
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I have the exact same problem with my 99...I am going home to try out many things. My idle is high for the first couple of seconds or so "normal warm up" then when the water temp gets above 175 or so I start to have this exact problem as well. Would it harm the motor if you just sprayed light amounts of carb cleaner / brake cleaner onto the IC piping, if the motor changes idle you just found a problem spot right?
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Old 01-11-2008, 07:52 PM   #14
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You can do that without worrying about harming the engine. That is an alternative to the links I posted above.
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Old 01-11-2008, 08:10 PM   #15
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is there still black coating on the butterfly?
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Old 01-11-2008, 10:00 PM   #16
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Quote:
Originally Posted by 99NBMia View Post
I have the exact same problem with my 99...I am going home to try out many things. My idle is high for the first couple of seconds or so "normal warm up" then when the water temp gets above 175 or so I start to have this exact problem as well. Would it harm the motor if you just sprayed light amounts of carb cleaner / brake cleaner onto the IC piping, if the motor changes idle you just found a problem spot right?
Spraying carb cleaner around places with possible leaks is a good way to search for leaks. If the engine surges when you spray in that area it could be sucking the cleaner in causing it to run a little different. If you want to actually clean the throttle body you should take it out. There are many parts not easily cleaned without taking it off.
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Old 01-12-2008, 02:19 AM   #17
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i just bought a throttle body to replace my own and it comes with a IAC unit. maybe it will fix the problem i tried cleaning it. ever since i gave it once the problem was present. maybe the IAC got stuck and does not work any more. i will start with that. also will do the carb cleaner test again. wish me luck.
-jasko
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Old 01-13-2008, 11:46 PM   #18
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my idle now is fine, it returned to the correct idle after I found a slight coupler leak using the brake cleaner along with rotating the idle screw a bit.
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