I came across this from another thread ... great info.
I'm trying to do this, but I can't find the IAC bleed screw. Is it on the end opposite the connector? Mine has a white round thing on the end ... I wonder if some of them aren't adjustable?
VibrantRedGT said:
Try resetting the idle again. Here is tutorial.
'94-'95
Begin with a cold vehicle. The idea here is to get the car to a firm cold idle with enough air bleed capacity left in the idle circuit for IAC adjustment.
The idle stop should be set first. Back out the idle stop screw, away from the bell crank arm, until about 1/2 turn past the point where it no longer makes contact (blade fully closed). Using an 0.010" feeler guage, tighten until gauge just drags between screw and bell crank arm. Remove feeler gauge. Tighten screw exactly 1 1/2 turns. If the screw is very loose, put a drop of loc-tite or silicone on it, so it doesn't work out of adjustment.
Now remove the connector to the Idle Air Controller (IAC) just on the other side of the throttle body. Start the car and allow vehicle to warm for 2 minutes. Give a small "blip" to let it settle. If it is having a hard time staying running you may have to get an assistant until you can get to the front of the car. Now open or close the air bleed screw (CCW opens) next to the IAC until the car idles at 575 to 600 rpm. For guys with aftermarket cams and an EEC tuner, you might want to idle a bit more briskly, say 650 to 675.
Obviously, this rpm range is by what the car and driver wants...ie, no set idle speed, whatever works for YOU.
Turn off the car. Now count the number of turns clockwise to close on the idle air bleed screw. If it falls between 1/2 and 2, it's okay, now reverse it out the same number of turns. Log the number somewhere in case you need it for the future. Reconnect the IAC. You are done.
If the air bleed screw is above 2 turns, it's a good idea to tighten the idle stop screw another 1/2 turn, then repeat the idle setting. If it is below 1/2 turn, then loosen the idle stop screw by 1/4 to 1/2 a turn, and repeat the idle setting. Be sure to put another drop of silicone RTV on the stop screw if it was disturbed. Reconnect the IAC. You are done.
Another variation for the 94-95 cars is to reset the idle in the procedure listed above and get the car to idle as low as possible with idle control OFF and the IAC unplugged. (around 600-650 rpms). Then plug the IAC back in, turn off the engine and unhook the negative battery post for 20 minutes. Then hook everything back up and put the desired settings in the PMS for idle control ON. Start with the percentage around 40% in the PMS air bypass setting and work from there. Once you set the desired idle RPM in the PMS, save and start the car. After a minute or two it should be able to control the idle.
I'm pretty sure the IAC bleed adjuster screw is on the part of the IAC where it sort of goes to a tip, mine has some white stuff on it aswell, but if you have a 94/95 which you do, it's moveable, tigthen it in all the way, then back it out 2 turns and then go to your idle stop screw.
the white thing i'm talking about is here -- if the wires weren't in the way, you would be able to see it on this end (where the yellow arrow is pointing) of the iac:
i dug the white thing on the end of the iac out with a knife. it was like gasket stuff. there was a head for an allen wrench under the white stuff, but it wouldn't turn and i stripped it, so i put sprayed the iac out with carb cleaner, put rtv in it and put the iac back on.
i have the screw in the throttle body (the red arrow) completely closed.
i have the iac disconnected.
i have the throttle stop screw so that the throttle is closed as far as it goes.
Personally I set the warm idle where I want it (you know the cold idle will be fine otherwise). Setting the cold idle and hoping the warm idle is ok is backwards if you ask lil' old me. This method is referenced in the bottom of that write-up.
The bleed screw cant be used too much or the idle will hang. This is another reason to use the latter method (the latter method is how to set MAF fox TB/IAC's as well. For SD it is different).
I have played around with this stuff quite a bit myself.
For those who cant get the idle down far enough, even with the bleed run all the way down (aftermarket TB's with a 1/4" hole drilled in the throttle blade can even even keep the idle high), a b-off plate like R.J. uses (and made a batch of for fellow SN'ers) has reportedly helped.