IWE again.
 

I've replaced one IWE which was bad, I replaced the actuator. I've hooked a vacuum pump up to the other IWE it holds and doesn't bleed down at all same as the other side. Yet still when I accelerate sometimes going down the road my driver side wheel make a grinding sound like it tried to engage. I checked the check valves both seem to be working as they should. I've checked the vacuum box behind the battery its intact with no holes or cracks. What else could this be? How can I figure out what is causing this?

test Vaccum while driving
 

Hook a vacuum gauge to tank side of the system and see if you loose vaccum get a idea how it works by using a gauge in between the vacuum components then you can fix it. Secondly is the IWE COMING ON when its not suppost to don't think it the case but keep it in mind.
Possibly one of the locks going bad at wheels haven't had alot of experience with this system but thats what I would do to trouble shoot.

Chris,

Check out this post by xjcamaro https://www.ford-trucks.com/forums/8...then-some.html it will give you a great step by step for checking out the IWE system.

Basically there are several sections that need to be tested. Solenoid, 2 valves, 2 actuators and a bunch of vacuum hoses. Hope this helps in your troubleshooting steps.

What you can do is take your vacuum guage, pull the vacuum line off at the engine. Use your tool to apply vacuum to the system just like your engine is doing. Pump it up and hold it and see if there is a leak down. If there is, start working down from there checking everything and applying vacuum. If there is a tiny leak in a line or hose somewhere it will leak down.

least system vacuum when accellerating
 

Chris, I am new to this IWE thing, but fresh on the trials and tribualtions. Probably your drivers side vacuum line system has a small vacuum leak somewhere. Seperate the drivers side vacuum system under the truck and install your gauge. Look under, behind the middle of the front cross beam there is a vacuum system pull apart connection there. Pump it up to at least 5-6. It should hold, wait for at least 15-30 seconds... it should not drop or there is a small leak somewhere giving you problems when accelerating and the overall vacuum supply is low. Good Luck

Well I've checked every thing from the vacuum box, to the solenoid, guess when the weather warms up a little bit I'll trace vacuum lines and find the hole. Wish me luck... I'll be posting up what it was once its fixed.

IWE vacuum supply
 

Chris, your leak must be a small one to only engage drivers side 4 wheel drive hub on accelleration. I dont remember... did you say the drivers side actuator holds vacuum? At least 6 inches or more for a minute or more without losing vacuum? Too bad we cant buy those factory vacuum harnesses in sections. A right of left side only vacuum line system would be a handy headache saving buy. I did a vacuum line system replacement with the factory harness (checkvalves , vents and clips installed, all set to go) from the solenoid supply down to the wheels for about 85 bucks. Was easier than the alternative of tracking the potential leaks on my 2006 F-150. Good Luck, if you decide to do the vacuum line system replacement... pull it apart at the middle connector and follow the existing route--> one side at a time. It's gotta be easier than dragging the entire harness from one side to the other as I did.

What i did for mine, to eliminate all the time tracking down a bad spot in the vacuum lines. I bought a whole bunch of bulk vacuum line at the parts store, a whole bunch of vacuum adapters and fittings and re-ran all the lines, but ran them up under the cowl to get from one side to the other, so if i needed to get at them again i wasnt digging around under the truck. It was alot cheaper than buying new lines, quicker than trying to diagnose a bad section, and easier than trying to replace bad sections. I used a little bit of silicone caulking on all the connections just to make sure it was a airtight seal. I never had a problem with a line after that. Just a thought if you dont want to play around with all the factory lines.