intermittent/occasional vibration while accelerating

[sjwelds]

Hey guys, 2012 El limited 4x4

So every once in a while we are getting an occasional vibration and or howling noise, from the front end, while accelerating. As soon as we let off it goes away.

Is this more likely to be the IWE solenoid or the IWE itself?

Haven't tried it in 4auto yet. Just doesn't happen often enough to predict etc.

Thanks.

 

[07navi]

Hey guys, 2012 El limited 4x4

So every once in a while we are getting an occasional vibration and or howling noise, from the front end, while accelerating. As soon as we let off it goes away.

Is this more likely to be the IWE solenoid or the IWE itself?

Haven't tried it in 4auto yet. Just doesn't happen often enough to predict etc.

Thanks.

Not the solenoid, try it in 4wd on a straight stretch.

 

[Dustin Gebhardt]

So it only happens in 2H (or you've only noticed it so far while in 2H)? While in 2H mode, the IWEs should have vacuum applied to them and the IWEs should be dis-engaged. When you accelerate firmly, you can sometimes drop your vacuum pressure. Usually, this isn't a problem because the IWE/vacuum system has a large reservoir just for this occasion. However, a slight leak in the vacuum lines can quickly consume all of the stored vacuum in the reservoir and cause the IWEs to engage due to the lack of applied vacuum. I speak from experience as this exact combination happened to me. I eventually found a rubber splice adapter running across the front crossmember that had been partial worn through, which allowed just enough of a leak for the IWEs to engage when the engine was not producing enough vacuum (typically under load and/or higher RPMs).

If I were you, I would start troubleshooting the vacuum system. Using a vacuum gauge or hand pump:

1. Find your IWE solenoid (on my '07 is is attached to the fan shroud, passenger side). Remove the tube coming from the intake manifold. Connect your vacuum gauge, turn on the car, and make sure that you have good vacuum being generated.
2. Find your vacuum reservoir. Attach your vacuum pump to the nipple and pump it down to 15psi of vacuum. Hold it there and verify that you don't lose more than 1 psi per minute. (Don't quote me on those numbers; that's just what I recall from my terrible memory). A reservoir that loses vacuum overtime is faulty and should be replaced.
3. Remove the hoses at your solenoid. Find the one that goes to the IWEs. Using your hand pump, pull down roughly 15psi of vacuum. Again, hold it there and check to see if you lose vacuum over time. (This is where I found that I had a leak) If you find a leak, check each IWE by removing the double-tube at each IWE and connect your hand pump on the bigger nipple. Suck down about 15psi and make sure that the IWE can hold that vacuum for a good amount of time without losing too much vacuum.
4. Connect your vacuum gauge to the IWE side of the solenoid. The solenoid will have 2 nipples, one for the vacuum supply (the intake manifold and the reservoir) and the other goes to the IWEs. With your gauge connected to the IWE nipple, start the car and switch from 2H to 4A (or 4H). The solenoid should alternate opened/closed, and the gauge should change from zero to vacuum.

Early 2000's F-150's had issues with the solenoid getting too much moisture and had a redesign to shield it from water splashing in the engine bay.

Additional info on the IWE system here:

https://www.f150online.com/forums/a...u-wanted-know-about-iwe-system-then-some.html

 

[sjwelds]

So it only happens in 2H (or you've only noticed it so far while in 2H)? While in 2H mode, the IWEs should have vacuum applied to them and the IWEs should be dis-engaged. When you accelerate firmly, you can sometimes drop your vacuum pressure. Usually, this isn't a problem because the IWE/vacuum system has a large reservoir just for this occasion. However, a slight leak in the vacuum lines can quickly consume all of the stored vacuum in the reservoir and cause the IWEs to engage due to the lack of applied vacuum. I speak from experience as this exact combination happened to me. I eventually found a rubber splice adapter running across the front crossmember that had been partial worn through, which allowed just enough of a leak for the IWEs to engage when the engine was not producing enough vacuum (typically under load and/or higher RPMs).

If I were you, I would start troubleshooting the vacuum system. Using a vacuum gauge or hand pump:

1. Find your IWE solenoid (on my '07 is is attached to the fan shroud, passenger side). Remove the tube coming from the intake manifold. Connect your vacuum gauge, turn on the car, and make sure that you have good vacuum being generated.
2. Find your vacuum reservoir. Attach your vacuum pump to the nipple and pump it down to 15psi of vacuum. Hold it there and verify that you don't lose more than 1 psi per minute. (Don't quote me on those numbers; that's just what I recall from my terrible memory). A reservoir that loses vacuum overtime is faulty and should be replaced.
3. Remove the hoses at your solenoid. Find the one that goes to the IWEs. Using your hand pump, pull down roughly 15psi of vacuum. Again, hold it there and check to see if you lose vacuum over time. (This is where I found that I had a leak) If you find a leak, check each IWE by removing the double-tube at each IWE and connect your hand pump on the bigger nipple. Suck down about 15psi and make sure that the IWE can hold that vacuum for a good amount of time without losing too much vacuum.
4. Connect your vacuum gauge to the IWE side of the solenoid. The solenoid will have 2 nipples, one for the vacuum supply (the intake manifold and the reservoir) and the other goes to the IWEs. With your gauge connected to the IWE nipple, start the car and switch from 2H to 4A (or 4H). The solenoid should alternate opened/closed, and the gauge should change from zero to vacuum.

Early 2000's F-150's had issues with the solenoid getting too much moisture and had a redesign to shield it from water splashing in the engine bay.

Additional info on the IWE system here:

https://www.f150online.com/forums/a...u-wanted-know-about-iwe-system-then-some.html

Thank you so much for the detailed information. I'll post back if I resolve this issue. Don't hold your breath cuz it might be a while.

Thanks again

 

[07navi]

Vacuum hub problems are common because they require constant vacuum to stay dis-engaged. It reminds me of the cars I had years ago that had the hidden headlights, half the time they were showing because they required vacuum and didn't have it.