Spark Plug gap bent into electrode

[07M45sGUY]

Hello everyone i seem to have a pretty bad issue but cannot figure out what is wrong with my car. I have a 2007 M45s with about 135k on it. About 12k ago i did a tune up including replacing all plugs with OEM NGK #6240's last week i had a misfire while coming off the thruway and i also heard a marble sound in the motor. I pulled over to a gas station and added some oil. I drove the car about 8 miles the marble noise went away but bad misfire still there. Had the car towed home from work. Changed the plug in cylinder 8 and swaped the coils from cyl 7 to 8. About a day later misfired again and brought it to the dealer. So at this point its not the plug or coil. They pulled the plug out at the dealer re gaped it and drove it for about 45 miles and its driving fine. Said the injector is good as well. They are going to put a scope in it today and check for damage on the piston and do a oil change looking for any metal in the oil. I read up online that is could be the beginning of the motor letting loose but have NO IDEA, any suggestions will help thanks. PS i have a intake with a K and N on it and a megan mid pipe and cat back exhaust if that helps

[Ilya]

I can't comment on the motor, but I can guarantee that the filter and exhaust have nothing to do with this. You either have a bad sensor/electrical issue causing the misfire...or you have a physical motor issue unfortunately. Any check engine lights?

[Double E]

"About 12k ago i did a tune up including..."

What else was included? (all of it) Seafoam treatment too?

[EniGmA1987]

What made you think to swap the #7 and #8 coils? Ifthey were correct then swapping them would cause a problem no?

[Ilya]

What made you think to swap the #7 and #8 coils? Ifthey were correct then swapping them would cause a problem no?

This is done to test the coilpacks. If #8 is misfiring and you move the coil, the thinking is that if the coilpack is bad then the issue will follow the coil. If you move the coilpack and the issue remains in cylinder 8, then you have something else going on.

The other way to test coilpacks is to unplug them one by one (plugging them back in before going to the next one) while the car is idling. The idle should change (get rougher). If it doesn't, then you know that pack is dead.

[svard75]

Your title tells me that your plug was damaged because the electrode was mashed into the plug body. There's a few reasons that could happen. Original plug length too long, plug was threaded way too tight and you'll have to use a washer now, or you have something in the cylinder that hit your plug. Worst case your bearings are so worn the piston is moving more than it should or the pistons damaged. You may have to remove your heads to check what's in there and then plug length for that cylinder. Ill bet whoever did the tuneup used wrong plugs or tightened too much.

[07M45sGUY]

The only thing that i dont understand is that it went 70 miles before happening again. and if the bearings were so worn wouldnt it hit everytime. The dealer re gaped the bent plug (which is the second one that the tip has bent into the electrode) and they have driven it 60 miles and its its still ok. they have no answers yet so as of today its still there.

[svard75]

Well something could be in there. Did you ask the tuneup guys what the original plugs looked like? If some of the ceramic broke off and stayed in the cylinder it could explain your current condition. Driving it with that piece, if its still in there could be really bad. Imagine if it gets lodged in a valve and the piston hits the valve? You said they were going to use a scope to see inside the cylinder. Any news on that result?

[07M45sGUY]

Myself and my friend did the tune up and he has been working on cars for over 20 years. He is not a certified mechanic but we have done alot more crazy stuff then replacing spark plugs. I took the old ones out and all gaps were equal and no broken plugs or pieces missing. I used oem NGK plugs same ones i took out. we also replaced both belts i took it to the dealer for a coolant flush and a rear dif and transmission flush as well. I didnt do the seafoam treatment. i guess another thing could be carbon buildup that broke lose and floating around in the cyl and is causing the bent plug tip, but i didnt hear it rattling around the second time only the first time. Gonna call the dealer today and see if what the scope saw.