What does a loose spark plug sound like?

[Password]

Started getting a noise when I press the accelerator, let go and it stops. It almost sounds like there is some metal on metal grinding. There's no shaking or vibration. If I move my head over the armrest when accelerating, I can also hear the noise travel in the rear....like exhaust gas maybe? I feel like there is a loss of power, but the wife that daily drives it says it feels normal. I know it's not a blown plug, the sound I'm getting is different. Looking for a reason to not pull all the COPs and inspect each plug. It's at about 175k miles, if I do inspect, I might just change the plugs while it's apart.
No CEL codes show up in the scanner.

 

[Yupster Dog]

Started getting a noise when I press the accelerator, let go and it stops.

Is it only going down the road you hear the noise? Does it do the same sitting in the driveway?

 

[Hamfisted]

Yeah, if you can, use a stethoscope type tool to listen around the engine when it's just idling in the driveway. It could be a crack in the exhaust manifold or something else. The 3V motors aren't known for losing sparkplugs. When were the plugs last replaced ? Your first guess may be closer to being accurate. With the hood up, set the parking brake, put it in gear and see if you can duplicate the noise to better locate it.

 

[Password]

Yeah, if you can, use a stethoscope type tool to listen around the engine when it's just idling in the driveway. It could be a crack in the exhaust manifold or something else. The 3V motors aren't known for losing sparkplugs. When were the plugs last replaced ? Your first guess may be closer to being accurate. With the hood up, set the parking brake, put it in gear and see if you can duplicate the noise to better locate it.

I'll try that out. Changed the originals at around 100k.

Is it only going down the road you hear the noise? Does it do the same sitting in the driveway?

I've only heard while in motion and pressing down on the gas pedal but I'll try @Hamfisted 's test this evening when I get back home.

 

[Password]

I'm going to try again tomorrow, but there was no noise while parked in the driveway and pressing the gas pedal. I didn't hear anything using the stethoscope either but that could have been user error.

 

[Mylove-19]

It would run like a Harley Davidson i just blew 4 plugs out pass head and to put steel inserts in the head

 

[Trainmaster]

Exhaust leak, as was said or perhaps a rattling aluminum heat shield... Internal muffler damage and something rattling inside.

 

[lbv150]

Loose plug starts out sounding like exhaust manifold leak...ticking at idle at a drive through window and you can hear it well. It keeps progressing over time until....you need the steel insert if not taken care of sooner. The plug loosens to a point where there are not enough threads left and it strips the rest out from pressure.

 

[Password]

Rear differential? Pep Boys says that's what it is. I could hear what sounded like metal on metal rubbing on each other when I was driving next to it, but does that explain the noise up front and lack of power?

 

[Password]

Another shop confirmed it is the differential. He said not to fix it yet, that it wasn't making enough noise to be an issue at the moment but to bring it back if the noise gets louder. I'm getting a cost anyway, but Pep Boys said it would be around $4k.