What could bend a spark plug tab?

2007 Tacoma 4X4 V6 6 speed manual 152K miles. Tripped a P0305 Cylinder 5 Misfire. When i pulled the #5 plug the ground tab was bent over and just touching the center electrode. It didn't look smashed onto the electrode, just bent over causing a short. I re-gaped it and it runs good and the check engine light is off. However now there is a tapping noise coming from that side of engine like a valve tick at low RPMs and then I hear what sounds like a marble bouncing around in the cylinder but this noise only happens now and again. I did a compression test and it was normal 180psi. This just can't be good.

 

If you have access to a scope I'd pull the plug again and look in there.

 

Do you know if the cheap ones at harbor Freight are any good? Can you look up to see the valves as well?

 

Could be the 4.0 tick you hear, no?

 

That is what I thought at first but random pops like a marble in the cylinder is way more that the "Taco Tick". Something bent that spark plug tab. I installed the plugs 15K ago and I would not have bent it over installing it.

 

Did you change spark plugs not too long ago? If you are not careful feeding the plug down into the cylinder, the side electrode can get bent.

If you heard the bouncing marble more frequently, I would wonder if something fell into the cylinder when you reinstalled the plug, but you say it happens occasionally.

I also wonder if the "bouncing marble" is pinging?

 

Only time I seen that was on a 2 stroke string trimmer.
A piece of carbon dislodged from the piston and messed up the plug tip.

I'm not saying that is the cause of yours to be bent.
It is just the only time I've seen it happen.

 

The motor has inhaled something....either internally or something you did when you changed plugs. Either scope it or send an extendable magnet into the bore. Ground electrodes don't bend by themselves.
Cheers, jeff

 

If your ground strap was bent then expect to see damage in the combustion chamber of the cyl head . Something got sucked into the throttle body and into that cyl

 

15K on the plugs, I'm very careful feeding them down the tube and always check the gap. I'm no expert on engine noises but it's more like a door knock than a ping. I'll borrow or get a scope and have a look inside. I made a video when it was making the random knocking and someone in work said it sounded like a worn wrist pin slapping around.

 

US Marine is right on target. And I will add that whatever you are hearing bouncing around is possibly what has been sucked into the cylinder.

 

I would definitely scope it. Buy one, borrow one or rent one somewhere but I'd be ruling that out immediately.

 

I don't see how there could be anything bouncing around in a cylinder, he's been running & driving the truck. If there were something bouncing around in that cylinder, you'd already have a hole in a piston, bent, or burnt valve. They may be right, but my opinion, anything bouncing around inside a cylinder won't last even a minute, certainly not while you are driving around in it. Like I said, just my opinion.

 

Nothing is bouncing around. If there ever was something it went out the chamber through the exhaust valve.

 

Or firmly embedded into the combustion chamber

 

Yeah, this doesn't sound good- something found its way into the chamber and bent the ground. Like many have said, they don't bend themselves. And now you have a knocking sound, so it's probably not a coincidence. Take a look at the throttle body for a missing screw

 

I'm guessing a scope will show a piece of the ring land gone.

 

If it is a wrist pin when you rev up the engine and back off it will usually really rattle. You could have had a piece of carbon break off and bend the spark plug but it should have exited the exhaust port. Why it is an intermittent popping is the question. Better scope it and see if you can find anything. If something got in there and is bouncing around you will be able to tell in about 3 seconds when you put the scope down the hole.

 

You should see what kind of damage Holley carb throttle plate screws can do and they're 8/32 ×.25 or even a holley bowl vent tube . I know because I had that happen to me