Loud humming noise from Idle Air Control valve? - MustangForums.com



4.6L (1996-2004 Modular) Mustang Technical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within.

Reply
 
 
 
Thread Tools Search this Thread
Old 03-02-2011, 06:30 PM   #1
Brad1405
Thread Starter
 
Join Date: Mar 2011
Location: Florida
Posts: 2
Unhappy Loud humming noise from Idle Air Control valve?

I have a 98 Mustang GT with a 4.6. I have had a problem with the car wanting to idle up to 1500 + RPMs and making a loud humming noise. It does this at random times. Sometimes I'm just sitting at idle either in gear or park. I replaced the TPS sensor and the Idle air control valve. Now it has gotten worse. The idle problem has seemed to be solved but the humming noise is bad. Just sitting at idle it doesn't make any noise. If I rev it up it starts making the loud noise when the RPMs begin to fall. It does this just sitting still or while driving. I've had mechanics look at it and we've found that when we restrict the air flow (not completely) to the IAC the noise completely stops like the IAC isn't adjusting properly. It did this though with the old one and the new. I unhooked the new one and attempted to start the engine and the valve seems to be adjusting fine. I also tested the cables that go to it and they show 12.2 volts which is within the 10.5 to 12.5 volts that Ford recommeneds. I've showed this to Mechanics and life long Mustang enthusiast. No one can figure this out. This car is my baby and I really need some help. Thanks!
Brad1405 is offline   Reply With Quote
Old 03-02-2011, 11:36 PM   #2
cliffyk
TECH SAVANT
 
cliffyk's Avatar
 
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,929
Default

I am not greatly familiar with the '96 - '98 models, however is the plumbing to the IAC stock? On the '99 - '04 there is a Helmholtz resonator in the IAC feed line that is there to break up standing waves that can create the "honk" even with a good IAC.

Here's what I found when I sectioned my IAC after it developed the honk.

The other possibility is that you got a bad "new" IAC, that does happen now and then...
cliffyk is offline   Reply With Quote
Old 03-03-2011, 03:33 PM   #3
Brad1405
Thread Starter
 
Join Date: Mar 2011
Location: Florida
Posts: 2
Default

Quote:
Originally Posted by cliffyk View Post
I am not greatly familiar with the '96 - '98 models, however is the plumbing to the IAC stock? On the '99 - '04 there is a Helmholtz resonator in the IAC feed line that is there to break up standing waves that can create the "honk" even with a good IAC.

Here's what I found when I sectioned my IAC after it developed the honk.

The other possibility is that you got a bad "new" IAC, that does happen now and then...
I'm assuming the resonator your talking about is the plastic box that is in between the IAC and air intake hose and yes it is there. There is nothing inside that box. Is there suppose to be? I managed to make the noise stop by putting a hose clamp on the IAC hose and tighting it down so that it bottle necks to a third of it's original size.
Brad1405 is offline   Reply With Quote
Old 03-03-2011, 03:36 PM   #4
Donnie's GTS
4th Gear Member
 
Donnie's GTS's Avatar
 
Join Date: Jul 2006
Location: SoCal
Posts: 1,030
Default

I had the EXACT problem you have described, fixed with a new IAC. Basically rpms would shoot up 14-1700 rpms with a loud humming sound. Basically a quick rev would temporarily fix the problem. At one point I let it go, and my car shut off (assume it went into safe mode.)
Donnie's GTS is offline   Reply With Quote
Old 03-03-2011, 05:04 PM   #5
0949er
4th Gear Member
 
0949er's Avatar
 
Join Date: Mar 2009
Location: NC
Posts: 1,909
Default

bad iac. My buddy drove a taxi (had the 4.6 in it) with that hum... replaced the IAC and fixed it.
0949er is offline   Reply With Quote
Old 03-03-2011, 10:27 PM   #6
Mr.SVT
 
Mr.SVT's Avatar
 
Join Date: Mar 2011
Location: Virginia
Posts: 30
Default

what is a IAC
Mr.SVT is offline   Reply With Quote
Old 03-04-2011, 04:26 AM   #7
Mr.SVT
 
Mr.SVT's Avatar
 
Join Date: Mar 2011
Location: Virginia
Posts: 30
Default

Thanks it seem everytime I hear a noise it gones away the next day I'm like wtf
Mr.SVT is offline   Reply With Quote
Old 03-04-2011, 09:22 AM   #8
cliffyk
TECH SAVANT
 
cliffyk's Avatar
 
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,929
Default

That is the way it starts out, then as the vibration further wears the IAC valve centering vanes it get more frequent and louder--just replace the IAC and be done with it...
cliffyk is offline   Reply With Quote
Old 03-04-2011, 03:09 PM   #9
Mr.SVT
 
Mr.SVT's Avatar
 
Join Date: Mar 2011
Location: Virginia
Posts: 30
Default

Can anybody tell me where IAC is located on the car cause it sounds like its coming from the bottom or back of the engine is it a DIY or take to dealer
Mr.SVT is offline   Reply With Quote
Old 03-04-2011, 04:33 PM   #10
Airman21
2nd Gear Member
 
Airman21's Avatar
 
Join Date: Feb 2005
Location: OH
Posts: 294
Default

do a search on here for IAC you will find out all you need to know.. It is a DIY job no need to take it to dealer.
Airman21 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Spark Plug Change 2007StangV6 2005-2014 Mustangs 30 01-28-2016 06:09 PM
2005 GT Intermittent Low Rail Pressure Throttle Drop zanemoseley 2005-2014 Mustangs 6 09-06-2015 12:58 PM
03 V6 Mustang Ticking Noise Emblazoned General Tech 0 09-03-2015 10:45 PM
HELP A/C Wont blow cold, electrical 2008 cbird1177711 2005-2014 Mustangs 0 09-02-2015 04:12 PM


Tags
04, 95, air, control, gt, humm, idle, idler, loud, make, motor, mustang, noise, temperature, valve

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump


All times are GMT -5. The time now is 05:34 PM.