2018 Yukon 6.2 strange sound

[finston]

This issue started yesterday while driving. Engine light, loss of traction control and forward collision system.
Pulled into park and have a very rough idle. First thought was lifter failure, which I had almost two years ago to the day. But this noise was coming from underneath the driver floorboard. Sounds like metal rattling in the exhaust. Nothing like the lifter noise that I had experienced before and where the noise was pronounced in the valve area of the top of the engine.
The goes away at an idle, but intensifies when giving gas. It isn't rhythmic but more random. Does anyone have a clue what it could be? Code reader says misfire cyl 6. I got towed home and let it cool off. Started up, light was off and no noise. After idling for 10 minutes, misfiring starting again and the noise again. There's a video that you should be able to hear.

IMG_3995.MOV

drive.google.com

Thank you all

 

[Joseph Garcia]

My guess is that you've got a failed cat with parts inside being moved around by the exhaust gases.

 

[finston]

After gettinf under there today the noise is coming from the bell housing. Looking more.

My guess is that you've got a failed cat with parts inside being moved around by the exhaust gases.

This issue started yesterday while driving. Engine light, loss of traction control and forward collision system.
Pulled into park and have a very rough idle. First thought was lifter failure, which I had almost two years ago to the day. But this noise was coming from underneath the driver floorboard. Sounds like metal rattling in the exhaust. Nothing like the lifter noise that I had experienced before and where the noise was pronounced in the valve area of the top of the engine.
The goes away at an idle, but intensifies when giving gas. It isn't rhythmic but more random. Does anyone have a clue what it could be? Code reader says misfire cyl 6. I got towed home and let it cool off. Started up, light was off and no noise. After idling for 10 minutes, misfiring starting again and the noise again. There's a video that you should be able to hear.

IMG_3995.MOV

drive.google.com

Thank you all

 

[persistent]

i recently had a consistent misfire on cylinder 8, and i learned the hard way that you should always do compression and leakdown tests to confirm the cause.

do you have any other codes beyond the P0306 for the cylinder 6 misfire? is the check engine light solid or blinking?

having spent a fair deal of time under this car recently, i suspect that mr garcia is right to point to the exhaust.

if you have the skills to do it yourself, pulling a few spark plug wires and spark plugs then doing a compression and leakdown test would narrow down the cause of the misfire. the kits for these are cheap on amazon, and i've found a TDC whistle to be a nice quick way to find compression stroke / tdc while doing leakdown testing.