Pics of the spark plug damage (opinions please)?

[DanO]

here is a thought, when the spark plugs were installed the one plug was not tightened all the way, when installing the coil it was tightened and broke off because off the plug being left loose, after some miles the plug loosened all the way out of the head bouncing on the tip closing the gap and causing the misfire. There is no way that a valve or piston could have hit the plug to do that kind of damage. Check the leakdown on the hole, if it is OK install a new plug and coil and enjoy your car.

yea, what he said!

1st , it is physically impossible to have piston/plug interference (assuming the piston is still connected to the rod).

2nd it is physically impossible for the timing to be so far off as to cause valve interference in one cylinder and not in at least one other cylinder.

look at the top underside of the coil pack—looks like the top or bottom (or both) of the sparkplug repeatedly hit this area causing the gouging to the plastic. I can think of no other reason for there to be damage to this part of the coil.

Alternative to Gerry’s theory: maybe the sparkplug hole in the head had been previously repaired due to an install error and the threads in the head weakened and finally gave up thus launching the sparkplug like a rocket out of the hole.

I agree with Gerry: do a leakdown and compression test on all cylinders and see what you’ve got. The rear head can be quite easily (relative term) removed w/ the engine in place.

If your mechanic doesn’t feel comfortable replacing the threads in the head then buy a good used head, clean it up and slap it on and enjoy!

Good luck and please keep us informed…let’s think good thoughts…

DanO

P.S. looks like you need a new coil pack too

P.S.S. you might want to check all the sparkplugs to help investigate...maybe the mechanic forgot to tighten the rear bank???

P.S.S.S. Wrong sparkplug size??

edit: fix Gerry's name (sorry).

 

[nsxtasy]

A big

to the technical gurus here who are spending their time trying to help Paul diagnose his situation!

 

[ncdogdoc]

A big

to the technical gurus here who are spending their time trying to help Paul diagnose his situation!

I cannot agree more, Ken. That is why I will always have an NSX and stay part of this community, because most everyone is there for everyone else.

 

[Larry Bastanza]

A big

to the technical gurus here who are spending their time trying to help Paul diagnose his situation!

I could not agree more also. Make sure when you do the compression test/leakdown you know the threads are good enough to seal the tool. Don't want to see a false alarm if the thread will not allow the tester o-ring to seal correctly.

I would think the head will at least need to come off and have an insert installed, if this is the issue. Hopefully that is all.

Good Luck,
LarryB

 

[Gerry Johnson]

Looking at the sparkplug thier isn't any aluminum on the threads, just the bottom threads look damaged as if it was not installed more than a few threads, also everything looks dirty as if it was leaking compression for a while, I don't think this happened all in at once. If it was my car I would look at the threads, if they looked bad I would take a sparkplug tap fill it with grease and chase the threads, the grease would help keep some of the aluminum from going into the motor, remember it is only aluminum and wouldn't hurt anything, if some fell in it would be very little and would just be burned out the exhaust.