Spark plug shot out of head!!

Well this is a little embarrassing but I’ll just come out with it. I’m in the middle of replacing my engine because I thought I had a vicious rod nock but last night while unplugging everything from the motor to take it out I realize I have my #1 or #6 spark plug (which ever is furthest from firewall) dangling from the wire outside of the head. So I now realize my knock was a piston slap due to lack of spark. The engine is tired and the cylinder walls are scored so I’m going to continue on with the replacement anyway.

Question: What would cause a plug to shoot out of the head? I ALWAYS torque my plugs properly, but I should mention that the plug was missing the electrode thing that sticks out the middle of the white porcelain that connects the spark to the arch. The threads on the plug are not stripped and the arch at the tip of the spark plug does not appear damaged from the piston.

It was an autolite copper plug bought from summitt racing with one ranger hotter that an oem plug for a 93 head.

Application: 87 renix 4.0 w/ a rebuilt 93 cyl head/intake/exhaust/and throttle body w/ renix tps adapted.

Thanks

THAT'S DIFFERENT....I've seen plugs that have shot the ceramic out of the steel seat....but a plug that came out entirely without stripping something....???? I'd have to say it was loose

The threads appeared unstripped. I forgot to try and screw it back into the head to see. I did tourqe it down when i installed it. BUT it was the second retourqing on the same crush washer. Does the absence of a fresh crush washer really make theses things come completely out after tourqing down? I have to think that the absence of the electrode in the middle of the ceramic had something to do with it.

So the spark plug unscrewed itself and the center electrode is gone, but the porcelain outside part is still in the steel shell? That defies logic. And I've reinstalled plugs without replacing the crush washer hundreds of times with no issues. How long ago did you reinstall the plugs?

Maybe 1000 miles on the reinstalled plugs. Yes the plug looks exactly as you described. It is bizarre. I'll try and get a pic of it tonight after work. I have a sneaking suspician that the center electrode just fell out into the cylinder because it was a flawed plug and the end result was that the plug came out. I'll have to double check the threads when i get home to make sure they'll screw back into the head to be sure its not stripped.

I suppose installing the same spark plugs more than once, could cause this. Since the crush washer was previously crushed. Could also be it was under torqued on the last install.

Personally i've reinstalled on various vehicles the same spark plugs 4+ times w/o an issue. could just be an odd ball thing...

Shot with DSC-T1 at 2009-06-08


Shot with DSC-T1 at 2009-06-08


No electrode in the ceramic...? I was able to screw it back in but it seems the threads were struggling more than before, when i took it back out it was slightly stipped.

Any ping (pre-detonation) before all of this? That's the only condition that I can think of that eats electrodes. In your case it would have gone on for quite a while!

I'll wager a beer that it was never properly tightened in the first place. Any takers?

1331 said he torqued them. Do you think loose plugs would cause the elctrode to evaporate?
The white on the plug seems to indicate pre-detonation.

EDIT: found this link the plug looks like yours...

http://ratmtent1.com/Autorepairblog/?p=22

hubs97xj said:

I'll wager a beer that it was never properly tightened in the first place. Any takers?

Click to expand...

ive forgot plenty of things, and it always seems to be the smallest things that ive done a billion times. But from the size of those photos i cant tell whats really going on there

According to the Champion site, the torque is important to aid heat transfer away from the plug. And he was using plugs that were one heat range hotter than stock. I don't know about you guys, but I never put a torque wrench on a spark plug in my life. Just snug them down real good!

SleeperXJ said:

EDIT: found this link the plug looks like yours...

http://ratmtent1.com/Autorepairblog/?p=22

Click to expand...

This may have been what happend to me.

I've never touched a plug without a torque wrench, its just habbit. Although I had been experiencing backfire through the intake, buty no pinging. I assumed it was from my junkyard tps that I adapted that was due for a replacement.

I didn't resize the pics because i wanted you guys to see the detail.

I had the #6 plug come out of the head on my original motor. The #6 piston came apart, so I was limping it home and the plug ejected itself. I am not really surprised, cause I could never get that plug out.

Reading that link, it's really difficult to believe Bud knows much about anything. Any arc damage on the exterior of the block? Threads in the head good? Does the engine launch good plugs from that cylinder? Does it run any better with a good plug?

This is the first time it happend. The threads in the cylinger felt rougher than before. It was a little tougher to put the plug back in. I had to use a wrench after maybe 2 roto's when I used to be able to hand turn it a lot more. I haven't ran it with another plug becuase everythings all torn apart as i'm putting in a newer motor now. I found the plug shot out after i tore down all the accessories/radiator. My cylinder walls are shot so its due for a replacement anyway.

Good luck with the replacement motor. Since you can't easily restart your engine this may be as big a mystery as what happened to Jimmy Hoffa!!!