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.

 

If the PCV pipe/tube is present on your engine have you checked that 90* fitting at the base of the throttle body? Those have been known to cause similar issues.

 

I'll go check now, do you know how many/what size hoses I'm looking for?

 

There should be just one PCV and tube originating from the passenger's side valve cover, possibly that tube is covered with insulation, looking somewhat like this new OEM version:

 

What engine, how many miles, original IAC valve?
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.

 

I agree on the elbow. This is common.

Also curious what engine.

 

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

 

6.8, sorry about that. I love both motors though, damn good IMHO

 

Argh. Yeah. Posted in the "Modular V10 (6.8l)" then here comes @CathedralCub to ask what engine it is. It was late and I was tired and apparently overdue for a brain recharge. I remember thinking that I was sure it was a V-10 for some reason but didn't see it in any of the posts, but I was sure for some reason!

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.

 

^^^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.

 

My oops, I thought this was posted in the "Excursion" forum.
Was more interested in how many miles and if the IAC was original.

 

No updates, been a lot going on and have my 6.0 back so it's going to be a few more days.

 

I was going to post it in the Ex forum, however, I might have forgotten to there so you almost had me