Idle adjustment

[50bomber]

Hey everyone,
I have a question concerning idle speed. It seems that mine is set too low, like 600 when I am fully warmed up and in gear. When this happens the car gets a case of "hiccups" and the idle seems to go haywire jumping from 500-1100. I tried turning the screw to raise it a bit to like 900 and it worked for a while, but then it automatically went down in a few days, what gives? Is the ECU compensating for increased flow via the IAC? If so, is there anyway to adjust this w/o a custom chip? i would mainly like to raise the idle so that I would get more charge w/ my UD pulleys, they seem to do it around 800 rpm and also the car shakes, lopes and chops way too much at 600 and is much smoother around 800-900 rpm. It is driving me nuts.
And thanks for the replies

 

[87AODGT]

unplug the IAC, adjust to desired idle with the idle set screw on throttle body, then re set the TPS to .95-.98 volts, and plug the IAC back in

 

[accidentprone86]

what is the IAC?

 

[50bomber]

IAC=Idle Air Control motor, its the cylindrical thing attached to the right side of the throttle body with a wire attached to the bottom of it. Anyhow, to 87AODGT, is that going to be permanent? If so, I will def try it.

 

[HISSIN50]

Here is a write up for cleaning the IAC and resetting the idle.

http://www.muscularmustangs.com/iac.php

good luck.

 

[davs5.0]

Maybe its just my car but when I unplug the iac the car stalls out. Is this a symptom of a bad iac or am i missing some other problem? Motor is the 331 in my sig.

 

[mr.b]

i can unplug my iac at idle and it will idle perfect, don't know if this will tell you anything. but my car is also completely stock.

 

[jrichker]

Maybe its just my car but when I unplug the iac the car stalls out. Is this a symptom of a bad iac or am i missing some other problem? Motor is the 331 in my sig.

The engine is supposed to die when you unplug the IAC. See the Sticky at the top of the forum "Help me create the Surging Idle Checklist" for more idle related problem solving tips.

 

[Scott_B]

i've found on my car that if i set the idle for say 750 with the iac unplugged, when i plug it back in, it idles at 900. If i set it at 900 unplugged, 1100 or so. no idea what would cause that eh?

oh fe years back i drove around with it unplugged. car idled better with it unplugged then plugged in. i was speed density then as well. no idea why though it worked that way.

 

[HISSIN50]

i've found on my car that if i set the idle for say 750 with the iac unplugged, when i plug it back in, it idles at 900. If i set it at 900 unplugged, 1100 or so. no idea what would cause that eh?

oh fe years back i drove around with it unplugged. car idled better with it unplugged then plugged in. i was speed density then as well. no idea why though it worked that way.

As you know, when you reconnect the IAC, the air it passes will increase the idle. driving with it disconnected is a down and dirty way to keep it running (a few modded SN guys have done that as well - Andy comes to mind) and I think JRichker once told a story about a guy (Ken?) who was about ready to drive his car off a cliff after having tried many tricks to remedy such an issue.

some guys choose to set the idle so that the car idles w/o the help of the IAC - some write ups also have one set their idle this way. use whatever works is my thinking. a vac leak can also keep the car idling with no IAC input.

 

[enyawix]

I can not idle I will try disconnecting my IAC. I got a new IAC and it did not help.

 

[93gtmustang]

Each time you reset your idle you should reset your tps. Your car should die when you unplug the IAC, that means it is operating properly
When your car is at the idle you want, turn the car off, disconnect the negative battery terminal,wait about 30 minutes, reconnect the negative terminal.This last part is from my owners manual. It says to do this after the battery has been unhooked. Start car let idle for 1 minute. Turn off. Drive 10 miles in stop in go type driving so the computer can relearn the new idle setting. I really don't think the steps covered in the below link are necessary. I've done it that way and all those steps, turning off turning on, accesories don't really do a thing. ttp://www.muscularmustangs.com/iac.php
Also ,there is a part on this site that says to clean your MAF sensor with throttle body cleaner. Don't do it. I killed my sensor doing this. Quick dry electronics cleaner or lightly with a swab and alcohol.

 

[jrichker]

I can not idle I will try disconnecting my IAC. I got a new IAC and it did not help.

See "Help me create the Surging Idle Checklist" at http://forums.stangnet.com/showthread.php?t=534062
for help with your idle problems. The first post contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions.

 

[Roland69]

www.50tech.com has a good writeup on idle adjustment