Heightened exhaust noise that calms when changing throttle position on 2012 5.4L

I have a 2012 5.4L that looks and runs like new however during cruising at speeds above say 35mph will sporadically display an increased exhaust noise from up front, almost as if unburnt fuel is being introduced into the exhaust system and being ignited by the cat converter(s?). Changing throttle position slightly makes it go away. No loss of power, no pre-ignition ping, no backfire, no check engine light... just this heightened diesel like rumble. I have tried higher octane fuel especially if towing heavy and it doesn't seem to make a notable difference. This happens both towing and unladen. Checking for trouble codes with a Fixed OBD2 device shows no trouble codes. I also live in an E-Check county in Ohio where bi-yearly the vehicle is scanned for emissions-related trouble codes, always passing inspection. I have thought of possible cam phaser issues possibly letting ignition happen with exhaust valves not fully closed... Would or could cam phaser issues evade consumer-end or even more professional trouble code readers? Does this sound familiar and should I be overly concerned???

When my 06 had a cam phaser actuator act up the car ran terribly. It immediately threw a trouble light and died at the first stop.
I would have the exhaust manifold to cylinder head studs inspected if you can change the noise with the throttle. It is common to have passenger side manifold studs fail when the manifolds have high miles on them.

Does the 2012 have variable length intake runners??

I have a 2012 XLT, and believe it or not it may be an easy fix. Ford uses two metal bands that secure a heat shield by the cats. They will fail after time due to rust. When you’re traveling at that speed, the shield and clamps vibrate and you will go crazy trying to figure it out. I was able to spot it right away and repaired it with a stainless steel band clamp. Worth a try.

JamaicaJoe said:

Does the 2012 have variable length intake runners??

Click to expand...

That I don't know... The intake manifold is pretty well buried beneath covers, throttle body, etc. I could probably find out through some research. What's your thought???

The intake manifold is pretty well buried beneath covers, throttle body, etc. so (I) certainly can't tell by looking at it but could probably find out through research... What's your thought??

I have a 2013 with the same issue where the band broke on the exhaust as pictured in the above post. I fixed with a hose clamp.

Ford says you have manifold flappers just like my 06.

I have a 2012 XLT, and believe it or not it may be an easy fix. Ford uses two metal bands that secure a heat shield by the cats. When you’re traveling at that speed, it will vibrate and you will go crazy trying to figure it out. I was able to spot it right away and repaired it with a stainless steel band clamp.