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car wont idle with the IAC unplugged,

  • Thread starter Thread starter aar0s
  • Start date Start date Sep 21, 2011

aar0s

Founding Member
Dec 20, 1998
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69
Sep 21, 2011
#1
  • Sep 21, 2011
  • #1
I was trying to bump my idle up using the method in the surging idle checklist and as soon as I unplug the IAC the car dies, it wont idle at 600 at all. I had a vacuum gauge on it at the time and was showing steady vac so im not suspecting a leak, what else could be causing this?
 

LarsD

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Jul 2, 2002
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Sep 21, 2011
#2
  • Sep 21, 2011
  • #2
Throttle blade not open far enough? :dunno:
 

aar0s

Founding Member
Dec 20, 1998
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Sep 21, 2011
#3
  • Sep 21, 2011
  • #3
Its an aftermarket TB (accufab) so i guess thats possible.
 

4rdnut

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Dec 14, 2010
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Sep 22, 2011
#4
  • Sep 22, 2011
  • #4
The base idle reset procedure is a big waste of time, its much easier to just turn the idle screw up a quarter turn with the engine off and negative battery cable disconnected to erase computer memory, much easier this way. The computer operates the air valve inside the iac via the iac's solenoid and when you disconnect the electrical signal the valve shuts off the extra air that keeps the engine idling, just turn the idle screw up, its not rocket science and when you change the idle, the tps voltage will change so you have to readjust the throttle position sensor, set it at .85 volts and your done.
 

Mustang5L5

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Sep 22, 2011
#5
  • Sep 22, 2011
  • #5
If it stalls out when you unplug the IAC, it means you need to open the throttle blade more. You are basically idling via the IAC.
 

jrichker

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Sep 22, 2011
#6
  • Sep 22, 2011
  • #6
aar0s said:
I was trying to bump my idle up using the method in the surging idle checklist and as soon as I unplug the IAC the car dies, it wont idle at 600 at all. I had a vacuum gauge on it at the time and was showing steady vac so im not suspecting a leak, what else could be causing this?
Click to expand...

Turn the screw 3-4 turns and try again. Keep turning the screw until you get a sustained idle with the IAC disconnected, and then set it according to the instructions in The Surging Idle Checklist.
 

jonbacon

Member
Sep 12, 2011
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Sep 22, 2011
#7
  • Sep 22, 2011
  • #7
where do you turn the screw at on my 92gt. I think this will fix my idle issue???.. then how would I adjust the tps?
 

jonbacon

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Sep 12, 2011
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Sep 22, 2011
#8
  • Sep 22, 2011
  • #8
I guess I mean, do I just do like most people ...loosen 2 screw then make sure volts are right and if not turn it a little till the volts are correct..am I right for adjsuting this, ive never done it or turned the screw on the IAC, but took the battery off when I put the headerrs on and every since the car had a bad idle...and all parts are new, IAC<MAF<TPSS...
 

4rdnut

Member
Dec 14, 2010
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Sep 22, 2011
#9
  • Sep 22, 2011
  • #9
turn the idle screw thats on the throttle body arm bracket, just follow the accelerator cable to the throttle body, the tb arm rests on the idle screw, turn the idle screw a little over a 1/4 turn, then loosen the tps screws and hook up the voltmeter to the green and black wire and any voltage between .60 and .98 is good. adjust the idle first then adjust tps and remove negative battery cable to erase computer memory.
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,260
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Massachusetts
Sep 22, 2011
#10
  • Sep 22, 2011
  • #10
How to "set" TPS

http://www.stangnet.com/mustang-forums/825424-adjusting-your-tps-0-98v-not-necessary.html
 

jonbacon

Member
Sep 12, 2011
125
1
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Sep 22, 2011
#11
  • Sep 22, 2011
  • #11
got it, thanks.. gonna do a reset then actually adjust it. right now I am driving around with the MAf unplugged .. so i will reset it all then crank and let it idle for a few mins, then set it all... sound good???
 
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