Anyone know what could be causing this scraping?

[kaositic]

(2016 mustang ecoboost performance) So for reference my check engine light came on saying “system too lean bank 1” error code P0171, and there’s a rattling/scraping sound in what seems like it’s coming from the heat shield or exhaust. Anyone know what could be causing the scraping? Thanks for reading

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[Skye]

I don't have an answer. I'm processing, but...

The physical sound makes me think like you commented: a heat shield or connector has come loose.

But I also need to consider the P0171 code that occurred.

So I wonder if your problem is related to a O2 sensor, cat or something else which failed inside?

With the exhaust system cool to the touch, if you tap/band around with your hand, is it more obvious, something loose (heat shield/bracket)? Or does it sound like an item is rattling around inside the exhaust system?

 

[GR1MxREAPER]

Man those cars sound terrible in general.. sounds like a muffler baffle broken inside. The code I have no idea. Was gonna say severe false knock because of the vibrations maybe but that’s way to far away from the engine or sensors. Good luck

 

[ORRadtech]

Kinda hard to tell exactly what you are looking at right there. Maybe pan around a little bit.
Bank 1 is the only bank on a 4 cylinder engine. Other than the CEL you don't give any history. What is your milage? Any modifications, tunes, etc? What was going on when the CEL came on? How long have you been hearing the noise? Did it start before, after or at the same time as the CEL?
Noise possibilities are; something physically touching the car undercarriage, a loose baffle in the muffler, loose/broken substrate in the cat, a failing turbo and broken or loose parts of the exhaust or mounting system. It could even be a failing fuel pump making noise.
Lean Bank one could be low fuel pressure, a bad fuel pressure sensor (the high pressure sensor is a known issue), a bad/weak cat, O2 sensor, etc.
You need to put a scan tool on and find out what the fuel pressure is and what the fuel trims look like as well as boost.
There are probably other things I'm missing but basically it could be very simple or it could be very bad and we don't have enough information to really help.

 

[kaositic]

“With the exhaust system cool to the touch, if you tap/band around with your hand, is it more obvious, something loose (heat shield/bracket)? Or does it sound like an item is rattling around inside the exhaust system?”

That’s the weird part, I spent a some time under the car looking for rattling or something loose, I can’t seem to find it. This leads me to believe it might be an internal component gone bad or something.

 

[kaositic]

Kinda hard to tell exactly what you are looking at right there. Maybe pan around a little bit.
Bank 1 is the only bank on a 4 cylinder engine. Other than the CEL you don't give any history.


So it started at least a couple of days to at most a week before the CEL came on, I haven’t driven it much since. Mileage is 100k and it’s stock. Thanks for the help regardless, I’ll get a pressure test done.

 

[Skye]

That’s the weird part, I spent a some time under the car looking for rattling or something loose, I can’t seem to find it. This leads me to believe it might be an internal component gone bad or something.

Might be time to disconnect the exhaust and take a peek.

I am noticing two sounds. Maybe you have to.

In the video, there is one sound immediately near where you took that clip.

I'm also hearing a second sound, in the distance, off camera.

You've got the one code.

How are coolant temps? Oil level, oil color, coolant level and coolant color appear normal?

 

[Rebmo]

Cracked catalyst? Had that in a tundra but I took the converter over some rocks.

 

[kaositic]

Might be time to disconnect the exhaust and take a peek.

I am noticing two sounds. Maybe you have to.

In the video, there is one sound immediately near where you took that clip.

I'm also hearing a second sound, in the distance, off camera.

You've got the one code.

How are coolant temps? Oil level, oil color, coolant level and coolant color appear normal?

See that’s the weird thing everything looks good, coolant temps while driving are normal, oil color and level are normal and coolant hasn’t gone down or changes color, I’ve noticed that it doesn’t make the noise during idle and only when I accelerate or rev which leads me to think it’s related to the exhaust.

 

[sk47]

Hello; First thing that stands out to me is the code for running lean. That is more worrisome than a noise in my opinion. A lean run condition can wind up with engine damage.

That said I have had such noises for two reasons on cars I own and a third on I traced down on someone elses car.
One rattle was the heat shield out the outside of a catalytic converter. I stuffed some mineral rock insulation between the converter and the shield. A converter is in essence a stove to burn off excess fuel at high temperatures so gets very hot. The shield is in place to help keep from catching grass, weeds or leaves on fire. A friend high centered his jeep in a dry Texas field and the jeep burned up.

Another rattle was from loose baffles inside a fairly new muffler. Some mufflers have such baffles. I guess a CAT can have stuff come loose inside also.

The third thing was due to an engine rocking on it's motor mounts when driving. The exhaust was touching a chassis. A normal thing due to the torque of the driveline. Might take a look at the engine mounts.

 

[Skye]

See that’s the weird thing everything looks good

So, that's promising.

As general examples, attached are two photos.

In the first, a cat which has failed. In the second, the internals of a muffler/resonator.

If everything keeps leading you back to the exhaust, pick the closest point to the noise where there's a joint, disconnect and take a look.

An exhaust place might charge you an hour of labor to do this? Maybe two. But if they see something and confirm a repair is needed, then it's rolled into the repair bill. These shops see issues all day long. Maybe they can give some insight before going into the system.

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