idle issues

stock idle is 650rpm

Try reseting his idle like this:

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 a 0.010" feeler gauge, 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, and 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.

Maybe try resetting the computer first. You put a new part on, but it's trying to use the old data. Resetting will erase the old data and force it to learn the new stuff at a faster rate.
(Disconnect the battery for a few minutes...)
Dennis

MustangvertGT said:

what is stock idle supposed to be at? I just replaced the IAC sensor due to it idling high and holding revs. Its fine now, but when i give it the smallest rev, it will come down, then DOWN and back up. It wants to die (but hasnt yet).

basically it iwll go to normal idle (about 600) then drop to about 200 and jump back up. Does this everytime.

Also, any way to raise th eidle a tad? It feels like its too low. At first take off, it feels liek it wants to die.

I think it was better off with messed up IAC holding rev's at 1300 :-/

Click to expand...

I had the same problem, the car was idling at 650 PRM on my Autometer tach, I reset my base idle to 750 RPM and the hot start surge and die stopped. Here's the link to the base idle reset: http://www.muscularmustangs.com/idlereset.php
Tim

Dumb question, but did you index the IAC appropriately?

Are you sure you dont have any vac leaks?

Good luck.