Hey guys. I was hoping to get some help.
I had my truck running great at one point, with just about no issues.
I took it wheeling and got it stuck in water for a good 20 minutes Before I got pulled out. Most of the front end was covered with water, so much that I had water in my cab. That day I pulled the air filter out because it was soaking wet, and I barely made it back home because the truck had no power.
The next day it ran a bit better but it hasn't been the same
​​​​​​since, it's sluggish and no power. Eventually the Afm flapper started flapping around and makes lots of noise, to a point where Im scared to drive the truck.
Any input on why it would flap around like that? The flapping happens at medium throttle. If I floor it, it goes away.

 

Bump..
I'm still having this issue... Anyone?

 

New VAFM Maybe corroded connector/ wiring issues as well. But if the VAFM is rattling, it's junk.

 

So i just checked my oil. Turns out i had water in it since its been in the water.. i never bothered to check since i had just changed it right before that happened. Not sure it that would be causing the issue, tho its possible since the pressure would be different.

 

Waall… you oughta change the oil, for sure, but that ain't gonna stop the VAFM from banging.

 

Just drained and refilled the oil a couple times, Water seems to be gone but its still noisy. Iv'e tried replacing the whole air box from my buddies truck, It does exactly the same thing, Put my box on his truck, It runs normal. So im thinking it could be something electrical that leads there.... But what?

 

Are you sure the AFM is making the noise?

The only electrical parts in the AFM are a fuel pump switch, an intake temperature sensor and a resistive board that measures how far the flapper is open. It is quite possible that you got water in the AFM or into its wiring harness, but I would only think a mechanically sticky flapper would cause what you describe. You said that the AFM works just fine on your friend's truck, which is why I am wondering if you are actually hearing the AFM on your truck.

 

Yes, its 100% the flapper that is banging and making the loud annoying noise, I taped it open before a short test drive and there was no noise. . I'm guessing its opening and closing way to fast and uncontrollably. The engine itself sounds kind of OK for the most part, if i give it a little gas. It has a very rough idle, but im thinking that's part of the issue with the noise. And of course i have almost no power.
At this point, i'm thinking that the cold water warped my exhaust manifold while in the water, and now i'm possibly leaking so much exhaust that i'm loosing all my power and the flapper is going crazy. But how would I test something like that without pulling the Ex-manifold off? One of the first things i did after buying the truck was to resurface the exhaust manifold, and its a pain in the butt to get off.

 

You drove it nose in to a deep puddle, didn't check the oil chamber was free of water intrusion. You need to do a compression test to rule out bent valves and other catastrophic damage.

Assuming the o-ring on the oil dipstick is in good condition the next highest entrance point for water is the PCV system's intake which is attached to the air cleaner.

You did say the air filter was soaked, since it is in a sealed box the easiest way this happens is for the engine to be turning and sucking it in.

Which leads to "hydraulic lock" of the combustion chamber. If this happens with any meaningful rpm it tends to break a major piece, like for example blows a hole in a piston or knocks a large chunk out of the side of the block..

 

The only way I can see what you describe happening to your Truck is if the engine has internal damage, probably from hydraulic lock as Co_94_PU said above. This internal engine damage is causing vacuum pulses in the intake because there is a large vacuum / combustion leak in the engine. With these vacuum pulses, the flapper opens and closes with the fluctuation of vacuum from no vacuum to normal vacuum.

Either that or a very strange EGR pulsation...

That is all of the guessing I have for tonight.

Just to be clear, there is no motor in the AFM that could cause the flapper to move as you describe. Something, such as the movement of air, is causing the flapper to bang around, but the AFM cannot do that itself.

How long was the water in the oil?