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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

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Old Mar 25, 2002 | 09:51 AM
  #1  
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IAC

 
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Old Mar 26, 2002 | 11:47 AM
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IAC

Still have rough idle on my 1989 5.8L, have cleaned the IAC. If I unplug it the engine dies quick. I have read many of the old posts and some say when you unplug it the engine should die quick and that is normal, other say that the engine should shudder a little while and then die. Does anyone know for sure what should happen when you unplug it and how to tell if working correctly, Thanks Mike
 
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Old Mar 26, 2002 | 12:28 PM
  #3  
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From: Lee's Summit MO
IAC


You can test it, a local auto parts store hooked up the terminals with a 9 volt battery and if the plunger opens, it's working okay.




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Old Mar 26, 2002 | 02:28 PM
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From: victoria canada
IAC

i have a 1993 5.8 cant get rid of the bad idle .if i unplug my air by pass solenoid, the motor will slow down to about400 rpm but would not die.hope i find what is causing this
 
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Old Mar 26, 2002 | 02:36 PM
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From: New England
IAC

I guess that I should just join the group. It seems that there are quite a few people with this problem.

Maybe a new forum... The rough Idling 5.8s.

My 351 is in a 1995 F150 and it has a rough idle. I unplug my IAC and the idle goes down a little but it doesn't stall.

I will keep a watch for a fix.
 
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Old Mar 26, 2002 | 04:18 PM
  #6  
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From: houston, texas (now Berli
IAC

If you unplug the IAC and it doesn't stall, you have an air leak somewhere. Most likely the upper manifold is leaking where it sits on the lower manifold, common problem.
 
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Old Mar 27, 2002 | 11:19 AM
  #7  
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From: victoria canada
IAC

hey i agree rough idling 5.8 as a forum . i have sprayed carb cleaner all around lwr /upper intake and still came up empty ,tryed vacumm connections,had 2 diffrent shops try and locate they came up with either ecm or injectors .i figure the last owner gave up and sold it i may just do the same. scott
 
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Old Mar 27, 2002 | 04:48 PM
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IAC

As soon as I get the chance I am going to pull the new ICM I put in and replace it with the old one and check if the idle is still bad. It idle gets good again it is the new icm, possible different programing.
Mike
 
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Old Mar 27, 2002 | 05:39 PM
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From: ct
IAC

when you unplug the iac it should not stall. the rpms should drop to like around 400. if your engine wont start with the iac unplugged then you need to set your hard idle. just turn the throttle stop screw a little and keep trying to start the engine. stop adjusting the screw in when the engine starts and just barely idles. now plug in the iac and your hard idle is set.
 
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