[force-fed-snake]

so my 93 has always had a high idle... around 1000, annoying but livable beings how i havent made time to check it out.

so last week i threw on an exploder intake, cleaned the TB, EGR, IAC...etc checked out all vac lines everythin looks good. fire it up and now it idles at 12-1500... and has a "lean" pop around 3500-4000... runs fine on the bottom... runs fine on the top once it gets past its hicup.

so i start double checking everything... TB idle screw is backed all the way out i find... so i think vac leak. 2 cans of carb cleaner later... i got nothin. timing is 12*. TPS was .78... i adjusted it to max of .89, this could be my pos meter... but it has close to full input voltage at WOT 4.8 ish

pull the iac... plug the hole.... fire the car.... bam... "idles" 4-500. so i replace the iac thinkin it may be leaking. brand new one makes no change.

so im kinda lost. im sure its something retarded... but im not seein it.

the tb idle all the way closed throws me... i did however notice a 1/8" ish hole in the TB blade... that for some reason didnt look "right"... but i dont have another to compare it to. other than that... idk. any ideas would be great.

[fogged306]

Just unplug the IAC and see if the idle drops to normal. BTW, with the IAC unplugged the car should idle at about 700-ish. If it doesn't, adjust the idle screw until it does. You'll still need to find the problem, but that's how it should be.

TPS voltage is fine.

Some companies had a 1/8" hole drilled in the butterfly when their made, what kind of TB is it? Also what other mods does the car have?

[force-fed-snake]

idle screw is backed all the way out.... unplugged iac got no change. i pulled it off and plugged the iac holes(black gorilla tape across the gasket surface)... that got the idle down, so i figured it was the iac "sticking" or leaking... hence the replacement. with brand new one i still have no change.

mods are minimal....stock long block, catless x pipe/exhaust, exploder intake, smog delete. i assumed it was stock TB, i have no idea. it really sounds like a vac leak someplace.... im gonna try plugging off the manifold vac to the "splitter" log... thinkin maybe the CC under the fender may have somethin goin on... that the only place i didnt check with the carb cleaner.

[force-fed-snake]

well the manifold vac being capped had no change...

so what about a mass air problem?? anyway to test?

[FastStang91Lx]

Could have an intake gasket that slipped or is leaking. It will pull air from the lifter valley. Also, are you using an aftermarket tach? The stock one is junk and most times is off.

[fogged306]

Unplugged IAC should be the same as putting tape over the two ports on the TB. When unplugged it will be closed. If the idle drops down to 4-500 RPM with those holes blocked off, there's two things I see. The idle screw needs to be adjusted so that it hits about 700RPM like that, and you either have a bad IAC gasket, or possibly a defective new IAC. Either way, the IAC is where I would do some investigating.

[force-fed-snake]

im basing the rpm off my snap on timing light.... which reads about 300 less than the dash tach.

im gonna check voltage to the iac.... thats one thing i didnt look into before. i cant see the gasket being the problem... atleast not from the outside... carb cleaner would picked that out. i will dig a lil deeper in that area, then im gonna start swapping "known good" parts from a buddies stash.