HELP! 1 DYING ti HERE!!!

[marko]

last night while driving home (@ about 80mph), car started sputtering and shaking/vibrating suddenly... pulled over on the side, opened the hood AND FOUND ONE SPARK PLUG (2nd from the front) COMPLETELY OUT OF ITS PLACE/SEAT (plastic S.P. cover was pushed up as well) & the rubber S.P. insulation broken to pieces (near the plug itself)!
I detached the plug from the cable and it seemed that 2 out 4 electrodes (Bosch platinum +4) were ever so slightly bent in, but the threads seemed fine.. so I just screwed the plug back in, pluged the wire back on top & the car drove home just fine... bought NEW plugs and installed them after coming home...
this morning, drove to the gas station just fine (about 1-2 miles), got gas & was pulling out of the station, WHEN THE SPUTTERING SHAKING & VIBRATIONS STARTED AGAIN - almost stalling with NO power (as if I've lost a cylinder AGAIN)! except this time the plugs seemed fine and none of them were loose!
2 possible scenarios:

1- frayed/busted spark plug wire is bad & problem will go away after I get new wires (but why did it drive fine on the way home last night & partially this morning???)...

2- something wrong with the piston itself (cracked or detached from the rod & is pushing/poping the spark plug out of head) since the car feels & drives as it is indeed missing on cylinder (but if there is such massive/catastrophic engine failure, woulldn't I be able to tell by seeing much more damage on the plug or head itself???)...

Anyone had this happen?? Any clues on what the f*&^ is wrong with this thing? Do I need a new block/head?

Ps- one last thing... it seems like it takes less turns to tighten the plug that popped out vs. the other 3 (not sure if that makes sense or not)... like I'm missing threads on the head itself (since the plug seems fine).

[campaiar]

Since the business end of the dislodged plug was deformed, I'd say something hit it.

If that spark plug is still in the head, I'd pull it out and get a led on a stick flashlight thingee and see if the top of the piston is ok.

This is kind of difficult, but it can be done, and it saves you from removing the head to take a look.

[aceyx]

I could swear I replied to this thread earlier today.


This happened to me last December except I lost the plug completely and it took about 80% of the threads. A new wire and a threaded steel insert later and it runs fine.

[Mad-Machine]

I do not know about the bent electrodes.. but I have blown a plug out of an air cooled porsche head. It seems I had forgotten to tighten the plug all the way down. Like above, it took some of the thread with it when it went, it was just a matter of chasing them down and putting a new plug in.

[marko]

Originally Posted by aceyx

I could swear I replied to this thread earlier today.


This happened to me last December except I lost the plug completely and it took about 80% of the threads. A new wire and a threaded steel insert later and it runs fine.

yeah you did dude... sorry.
wasn't getting replies so I changed the title.

[marko]

Originally Posted by Mad-Machine

I do not know about the bent electrodes.. but I have blown a plug out of an air cooled porsche head. It seems I had forgotten to tighten the plug all the way down. Like above, it took some of the thread with it when it went, it was just a matter of chasing them down and putting a new plug in.

did that.. drove fine the same day, but it was dying again the next day.

so I ordered a new cable (frayed), and I'm hoping that will do the deed...

if not, sayonara! LOL

[marko]

'IT IS ALIVE!' lol HAHAHA!!

yes, it was just an ignition cable, thank god!

though, I'm still perplexed about the whole thing (plug jumping out and all)...

[aceyx]

Yeah. It's still a total mystery to me what happened in the first place. But I do remember this happened to at least two other people, not including us.

I'm really okay just blaming the cable.

[pdxmotorhead]

Totally common problem on Miata's Since it happend to friend of mine I've noticed ceveral with the same telltale outward dings in the hood.

Probubly due to the heat cycling of the head and its being aluminum. The Miata head looks a LOT like ours....

I have gotten in the habit of checking the plugs at each oil change to see that they are tight.

Dave