There is a 3rd vac line coming off my 4wd diff. It's rubber and splices to the same connection as pink and blue near ABS connection. What is this line for? Vent?

 

It's a vent, never mind.
I swapped out my IACV due to low idle issue (650). Didn't notice a change. Started to jiggle the PCV line while engine running and now I have a high idle that wont come down (950 rpm).

 

As long as you are shotgunning parts at it, go to the dealer and get a complete PCV assembly - valve, grommet, and everything from it to and including the rear elbow.

 

I'm not shot gunning parts at it. I am reading an idle of 650 which is out of spec. I had learned that this is usually due to a faulty IACV. I had already cleaned it, So I replaced.

Summary of the night:
Replaced IACV.
Discovered small crack in bottom of 2WD solenoid. Replaced with a used one.
Reinspected vac lines.
Swapped AZ PCV with a used OEM one I had. Much tighter fit in valve cover.
After driving around for 10 mi I'm back down from the high idle in park and getting LT of around +7.8%. When the idle was high, truck ran great and trims were all around +3.1% and the idle was only high in park. Not sure what caused that yet.

 

Disconnect the battery to clear out the memory and let it relearn.

 

The battery was disconnected for 10min or more, multiple times last night and definitely as the final thing before I was done for the night.

LT Trims were very poor this morning and I have a pending P0171/P0174 code now. Either I made the existing vacuum leak worse, or I added to the problem with either the 2WD solenoid or Used Motorcraft PCV (I could feel the PCV rattling/buzzing with my hand this morning when I arrived at work).

New PCV includes lines for $74 from Ford. The AZ PCV I had in there definitely had a different fit than the OEM one.

What is the process for inspecting the 2WD/4WD solenoids? Do I just measure vac at blue & pink lines at the actuator while in 2WD & 4WD? Although I went through and checked these components out previously, I still think there may be a vac issue with the front axle. I got great mpg while in 4HI during snow storm and also I feel some road noise from the front axle as if it were engaged or turning. I recently had the front axle in the air and checked for the front diff to be engaged when truck was on. Both tires spun independently. I do not see a changed in LT or ST trims when I switch from 2HI to 4HI.

 

Discnnecting the battery is not the way to clear codes.
What your doing is taking away what the computer has learned (perimaters).
It defaults to preset programs and waits to relearn.Probably why your getting readings all over the place.
After the fuel filter change did you run any cleaner through the tank?
Another source of "mystery" air leaks will be the botton injector o-rings.
Buy 2 sets (they only come in 8 packs)the top is the same as the bottom.
Lube them with cooking oil before install. Make damn sure the rail is fully seated on top of the injector and have someone eyeball those when you start.
Alot of gas will come out quickly if not and a good fire extingusher is to be handy.

 

Sure it is and it's a better way to clear and reset. Specially when it comes to air metering and AF's.

You don't necessarily HAVE to. It will learn either way. It's a quicker way to do it, specially when troubleshooting.

Other ways is to pull the PCM fuse or just erase the DTC from the KAM.

There isn't a right and wrong here. Just different/quicker ways to do it.

 

I have a code scanner so I use that to reset CEL. I disconnect battery for a quick way to see if my work is making progress.

I took the truck to a shop for a smoke test. Results were leak at the new IACV and the EGR. I exchanged the IACV. For a new one and swapped the EGR with an extra that came with an intake I bought a while back. I checked the EGR and it was holding vac when applied.
With it all back together and ~20 mi of mixed driving I am getting a steady +6.2% on the LT trims. Is that right? Shop suggested I come back in to make sure there are not more leaks. Also, my idle is still at 650, which is low. Do I have another faulty IACV?

 

On idle, is there any chance your rpm indication is not accurate?
The spec idle is 750 +/- 50 so your close.
Usually a Scanner is quite accurate over a dash tach.
On LTFT, once you clear or reboot the PCM, the LTFT is just what it means.
It takes well more than 20 miles to have the LTFTs have any good meaning.
It could even be zero for some time before the is enough data to begin to build a record either plus or minus.
.
The STFT is near instant Ox sensor output recordings.
The LTFT is a 'very slow' accumulation of STFT averages that builds those tables. You usally can't track the two just by watching them unless your a super man.
The LTFT tables 'moves' by adding or subtracting their values to, the regular fuel tables.
Right after rebooting the STFT are active as they need to be for FI control.
After long enough drive times and cycles; if you were to look at the last data stored in the Scanner at turn off, you would see the LTFT values but frozen STFT values when the motor is not running because there is no sensor output to cause change.
What i'm getting at is Long term and Short term values come about, two different ways.
.
I have a situation where my bank 2 is shifted close to 2 times the bank 1 reading but it's constant and nowhere near being out of limits.
There are no cylinder missfire counts for bank 2 so it's not due to unburned air from missfire.
The only things left is either an air 'leak' or an injector that is not quite perfect for metering fuel.
Is it worth chasing? No in most cases.
Bottom line is you have this ability with a Scanner to look at all the data so this makes you sensitive to everything that is not quite perfect but is GOOD enough not to be unduly concerned about.
Remember if the PCM does not set a code, no matter, it's still within 'legal specs' even though you can see the imperfect parts of the operation.
The systems, while very good are not and never will be perfect for any length of time as parts wear and age.
Good luck.

 

Thanks bluegrass. The RPM output I was using was on my code scanner. In the past I would see my LT trims fluctuate even after a week of driving 500miles for work., ill be patient and give it some time before I check them again. I will probably have the shop do another smoke test to check for additional leaks.

 

Not a reply, related question.

Been throwing these codes for a few months now. I cant seem to figure out what the heck is causing them.
I have changed the intake manifold after I confirmed that it was bad with the water test. Codes went away for a while, then came back and I found that the air intake was broken. I replaced it with a K&N cold air intake. I replaced the MAF at the same time. I replaced the plugs with motocrafts, and the coils with super accel coils. I have a new battery, fuel filter, and gas cap.
I have done a smoke test and saw nothing.
Truck drives great and didnt loose any MPG. I have intermintent shakes and drops in RPM which makes me think a vacuum leak. I have been told it may be the PCM but I really want to explore other option before dropping that kinda cash.
Hoping one of yall might be able to tell me where to hit next?
Thank you

 

If your having 171/174 codes, its long term fuel trim tables for both banks are out of limits too rich. Verify this with a Scanner.
.
This won't cause cold start issues because the motor is normally set rich at that time and coves it up.
After a few minutes of warm up, this condition can causes rough idle and stalling because the injection is rich when the motor doesn't need it.
.
The fuel regulator has vacuum control for just that reason, to separately reduce normal fuel 5 to 8 psi pressure at idle hence amount of fuel injected. As throttle is opened the vacuum goes down a bit and pressure raises to normal operating level. This action also does not affect cold start when the regulator does not have engine vacuum and pressure is at max during cranking..
Good luck.