Weird 4 cylinder noise at light throttle

[Gabe63]

I have 1k miles, 5.3. Twice now at very light throttle, maybe 25 MPH in 4 cylinder mode I head this metallic rattling noise. More or less throttle and it goes away. Any ideas? Not the normal 4 cylinder drone by any means. Metallic sounding.

[harrison725]

Maybe the v4 exhaust flap rattling?

[Gabe63]

I am not positive what the flap is but it sounds like a metal flap rattling. I have done some research and understand there is a resonator but I am not sure what it does.

[chuckl1218]

The Exhaust adaptive valve or "flapper" valve is aft of the muffler. It is a valve that closes to minimize the sound of V4 mode. There have been many reports of this valve causing a rattle sound or squeak as it opens or closes. You can force it open using a bolt through it or a hose clamp to see if this is the cause. There is also a resonator aft of the flapper which you can see through the passenger rear wheel well. In addition to the large muffler, these are all designed to keep the exhaust note quiet and consistent, making the transition from V8 to V4 and vice versa, very quiet.

[fondupot]

Does it sound like its in the cab? Like under the dash? Or like its outside the truck.

 

I am hunting down a rattle in V4 mode, but it comes from under the dash. And it goes away in V8 mode. I can also make it go away when it's making noise if I press on a certain part of the dash. Lol, wierd.

[Gabe63]

Mine sounds like it is probably the exhaust. It is in V4 mode at low RPM and very light to neutral throttle. I can make it go away by either taking my foot off the throttle or pressing a little more but still staying in V4. Like back pressure equalizes and is making something bounce. It just never happened until 1k miles...

[ewbldavis]

Love the fuel mileage, but sometimes unsure of the V4 mode. I've considered a tune to deactivate it.

[tnchevy]

My truck also makes a noise when in V4 and very light throttle. It is back pressure (or lack of) causing it. I didn't really notice it till I put on an aftermarket exhaust (dynomax VT ). The exhaust was alright but when doing 55 mph down the highway on a flat grade the new exhaust exaggerated this and actually made the truck shake a little. Gave it a little more throttle and it went away. Put my factory exhaust back on and things are back to normal but I now notice this sound when barely pressing throttle.

[Stars_Fan]

Anyone figure out what causes this noise? Ive noticed mine is starting to do his now.

[Gabe63]

Yes, I was fixed for 300 miles by my dealer. They performed PIP5228A, which I just read online saying it is for a 6cyl (mine is 8). The truck ran smoother than new for about 300 miles and now it has come back. I need to take it in again.