First of all, my car runs fine. (Most of the time) However, every once in a while, it will have strange idle issues. Last night for example, my car was idling in the driveway and the idle speed would shoot up to about 2000, then down to 300 rpms, then it would catch back up and idle normally (800 rpms). There are a few other things that happen occasionaly that i havent quite figured out but long story short, i dont like how the IAC works in my car.
I have an extra throttle body laying around that i would like to do a little R & D on. Is it possible to fill in the idle air port in the tb and use the butterfly plate opening as the only means of idle control? I could also devise some sort of way to have a port on the intake manifold that is controlled by some sort of idle adjustment screw. Does this sound do-able? I have crower 2's and spacing the throttle plate open doesnt entirely work all the time. Suggestions?

That blue car got me boobies once

Well you Obviously know that if you unhook/eliminate your IAC your ECU is gonna throw a CEL. But I get worried if mine Isn't on so anyways I'm thinking you could start with a tiny drill bit and drill a hole in your butterfly plate (like 2/64" or what ever the smallest bit you can find) since you have 2 TB's to work with. If the Idle is too low just move up one size and open the hole up a tiny bit. Keep doing that til you get a consistent Idle (800-900rpm). As for where to put it I don't know if it would be better to put it near the Middle or the edge of the plate but personally I'd just put it slightly below the shaft. Mind you I am going completely theoretically here so if you do decide to do it you should do a write up on it to tell us exactly what you did to it and how it worked out at each increment.

-Kevin

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95 Eclipse RS - Rolled
96 Eclipse GS - Traded
95 Eclipse GSX- Sold
01 Blazer LS 4.3/5spd dropped and clean DD
88 Camaro RS 361 CID with a 6spd and a bar 10 second street car on motor.

Yeah i guess the only way to know for sure if it will work is trial and error. Thanks for the input. Keep em comin

That blue car got me boobies once

how about you just fix/replace you IAC and save yourself alot of wasted time drilling away on something that probably wont work right anyways?

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2011 Nissan Xterra Pro-4x

2007 Kawasaki Ninja 650R

1996 Mitsubishi Eclipse RS-NX 75 shot, AEM CAI, P&P t/b and intake mani-SOLD

1964 Buick Electra 225-all original, all power options, 325hp, 445ft/lbs tq

You misunderstand. There is nothing wrong with the IAC. It's "normal" operation is what I beleive is giving me all the problems. For instance, when the computer checks the EGR function, it closes the IAC and takes the air from the EGR system. However, my EGR is blocked off already so when the computer closes the IAC, it has no source of air. I also run low vacuum cams and that is, in my opinion, a huge factor. I would like to aim for a steady, 1100-1200 rpm idle speed. Any other input?

That blue car got me boobies once

Thanks for the tips, Terry. As far as spacing the throttle plate to get a higher idle, it worked for a little bit but the ecu kept correcting with the IAC and bringing the idle back down into the normal range. I am also running an SAFC and i have a CEL 61 for map sensor so one thing i may try is bypassing the SAFC and running it like that for a while. The apexi unit is kinda sketchy anyway but it seems to work...

That blue car got me boobies once

You're running cams, blocked off EGR, and an AFC and you're having surging idle issues. Hmmm ... sounds familiar. Just an FYI, you can have the EGR blocked off, run the stock IAC, run the cams and have a perfectly good 800-900 rpm idle from experience. You don't need to remove the IAC or drill holes in your throttle plate either. Or replace it for some other crazy contraption either.

You're probably just running so rich from the lack of vacuum that it's screwing with your idle. Surging to prevent the car from dying, stumbling around at other times because it's choking itself from too much fuel.

Anyway, something to try. First make sure everything is actually working like Terry pointed out (MAP, IAC, CTS, etc) as they will all affect your idle as well. Take your logger and sit at idle. Log MAP values. You'll notice you are getting crap for vacuum. With your AFC start "leaning" out the 1000k rpm lo-throttle bin until the logger shows your MAP value close to the stock vacuum value (whatever it is ... I forget ... it's been too long since I had stock idle vacuum). Take the next few bins and slope the value back to 0% correction. This should help your idle.

In my car my idle is near perfect with the crower 2 cams and a ported head. I'm using a more advanced version of an AFC but it's just a voltage remapper (albeit a complex one). My idle sits around 850rpms which is just fine with me. Only issue I have is at 850 on the lope at night with all my electronics on, I drain the battery more than I charge it. Eh ... no biggie. I do have very rare issues when I throw an Issufficient EGR Flow code but that's easily fixed by clearing it with a logger.

-"Easy Mac"
05 Mazda RX-8 (RR8 #88)
99 Eclipse RS 398whp & 372lb-ft

Thanks for the extra info, Avenger. I will do a search and find the correct value for vac at idle and then search for a logger. This is a learning process and im enjoying every second of it!

That blue car got me boobies once

check for vacuum leaks too. i had a similar problem for like 2 years before i finally found an evap canister with a cracked off nipple for a vacuum line. jb-welded it and it ran like a dream

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99 GS-Turbo 3.55 MTX
S16G @ ~15psi - FMIC - Forged Internals
Clinton Township, MI

Status: Parting Out...

That blue car got me boobies once