Erratic idle issues (at idle)
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Lead Driver
Joined: Nov 2012
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From: Salem, VA
Erratic idle issues (at idle)
04 Excursion 4wd
Basically the title. The RPMs rise and fall (IACV I assume) when sitting still in either drive or park. I thought it was the driver's side valve cover pipe so I JB Welded the hose to the cover and no change. There is another one on the passenger side as well but it seems to be securely in place. Please tell me that someone in here has some ideas for me. Obviously, this is a vacuum issue, I just don't know which ones I should be looking at. I'm almost to the point of just parting out this thing and selling the chassis for someone looking for a Cummins swap donor. I love the rig more than any other vehicle I have right now but damn I'm about fed up.
Basically the title. The RPMs rise and fall (IACV I assume) when sitting still in either drive or park. I thought it was the driver's side valve cover pipe so I JB Welded the hose to the cover and no change. There is another one on the passenger side as well but it seems to be securely in place. Please tell me that someone in here has some ideas for me. Obviously, this is a vacuum issue, I just don't know which ones I should be looking at. I'm almost to the point of just parting out this thing and selling the chassis for someone looking for a Cummins swap donor. I love the rig more than any other vehicle I have right now but damn I'm about fed up.
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Lead Driver
Joined: Nov 2012
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From: Salem, VA
I'll go check now, do you know how many/what size hoses I'm looking for?
Fleet Owner
Joined: Aug 2010
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From: Reynoldsburg, Ohio
Fleet Mechanic
Joined: Feb 2011
Posts: 1,812
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From: Thousand Oaks, CA
Sounds like an IAC valve issue to me, too.
The IAC valve is not related to vacuum.
It is part of the throttle body bypass port controlling all the air entering the engine when the throttle body butterfly plate is closed.
There are no codes for a faulty IAC, maybe for the circuit wiring, but nothing for it being out of spec in function.
You can try cleaning it, but the electrical part inside may be faulty.
A leaking vacuum line can also cause erratic idle, but a vacuum leak allows more air into the engine that is not measured by the MAF so affects the air-to-fuel ratio.
Fleet Owner
Joined: Aug 2010
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From: Reynoldsburg, Ohio
Good question on the engine but as this was posted in the V10 sub-forum I assumed it was one of the Modular Motors, V10 or V8
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So I decided to ask. Duh!
LOL!
Yeah check that elbow and eyeball everything else to see if anything looks old, rotted, cracked, disconnected etc.
Fleet Owner
Joined: Aug 2010
Posts: 21,253
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From: Reynoldsburg, Ohio
^^^Been there, done that on the "did I miss that?" info! 
I recall the first time some 10-11 years ago I forgot to add pertinent information and got griped out big time---never miss stating what I'm working on: year, series, engine and fuel type these days.
I recall the first time some 10-11 years ago I forgot to add pertinent information and got griped out big time---never miss stating what I'm working on: year, series, engine and fuel type these days.
Fleet Mechanic
Joined: Feb 2011
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From: Thousand Oaks, CA
My oops, I thought this was posted in the "Excursion" forum.
Was more interested in how many miles and if the IAC was original.
Was more interested in how many miles and if the IAC was original.
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Lead Driver
Joined: Nov 2012
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From: Salem, VA
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