200 psi of flaming gas can push past.

 

How would a loose plug lead to detonation and broken plug electrodes?

 

Little leak past roasts the coil pack from the outside in. The coil pack can't "blow" off because of the retaining 10mm bolt on top of the coil pack. The rubber at the tip of the pack has enough "give" that it allows some flex, but everything pretty much is still in place.

Happened to me, too. The char on the coilpack suggests that flaming, pressurized gas makes it into the tube where the top of the spark plug and bottom of coil pack meet.

Also, I've seen fractured coil pack tips because of it. Not sure what exactly happens in terms of short circuits and ignition, but the secondary spark plug tip loss happens quite a bit with this (and very rarely do the tips fall off without this kind of problem... unless someone has tried to gap a non-gappable plug).

 

Like Billman says. Sounds like loose plugs to me as well. Ive seen the same exact thing before. Infact i bought a used car with a toasted engine from Honda that had this problem to a T :/ OEM original plugs on an 2001 in a car with 100k miles.

 

Other way around Rob. Detonation-broken-loose.

 

Ok, that makes sense, but what caused the detonation?

Someone give me the details of how a loose spark plug leads to total engine failure? It seems this is a well known phenomenon but I don't understand how it happens. Or are you guys saying the loose plugs & burned-and-busted coils are just a symptom of some other type of engine failure?

 

Ignition/detonation can be caused by fuel, fuel delivery issue, ignition timing, wrong plug, heat...etc.
Broken coil can cause issues since it does not seal any more and oil can get in plug hole which can cause misfire.

 

Air is pulled past the threads, leaning out the cylinder.

Tip of spark plug glows until it becomes molten and melts off.

Make no mistake, a loose spark plug will destroy an engine, and all the damage you see started with an improperly tightened spark plug.

The OP issue was caused by an improperly tightened spark plug, 100%. Not 99%

 

Finally opened this motor. Took head off to see what happen. Basically prongs on 3 spark plugs broke of (4 prong plugs, all 4 prongs broke of). There is no damage inside other than small dings on top of the piston from those little prongs hitting it. Car just stopped running and knocked because only one cylinder was still working. No broken retainers, no scored cylinder, no bent valves, everything looks good. 4 new plugs and it would run good again. Unfortunately spark plug threads in the head are stripped and will need helicoil. Since I sold car I have no use for motor and if somebody is interested I will sell it.

 

Posting back one year later, thats dedication! I had those installed in my car for 5 minutes and took them out and returned them. Those bosch four prong plugs are known for engine failure. YOU DO NOT NEED 4 PRONGS ON A SPARK PLUG. Period.. Cool idea but its garbage. Although in this case it sounds like improper torquing. Still waiting on billman to post back on his pull test