Spark plug insulator missing.

[kloppilt]

Do you guys know the extend of the damage done by a spark plug insulator?
I have a 91 Accord with about 190 k miles on it. A couple of days ago the engine lost power on highway. I limped for 2-3 miles and opened the hood. The number 3 spark plug wire was loose. I checked the spark plug itself and it was very loose. I took it out for observation and it was quite a bad situation. The insulator was missing and the electrode was worn for almost 2 millimeters.

I checked through the spark plug hole and couldn't see any pieces in there. There was no physical damage to the plug itself, either.

I've since replaced all of them - the other three were good. The card drives OK and there are no noises.

My question is, do these insulators evaporate? Or if they are crushed, do the pieces get out through exhaust or are they still in the cylinder scraping and wearing the engine out.

From what I can tell, the car is not burning any oil yet.

 

[Matt_S]

I doubt very much that it did any damage. It probably got pulverized and ejected out the exhaust valve. Given that you'd have to yank the head to really inspect this, I wouldn't worry about it. You don't hear any noise and there's no oil burning, so don't worry. That ceramic insulator isn't large or strong enough to cause any damage.

 

[RavenTai]

Saw a Toyota motor damaged by a spark plug, the whole tip of the plug broke off including the electrode, I helped tear it apart the top of that piston and the bottom of the head were badly chewed up by the electrode bouncing between the two at high speed, we found the 1/4" section of electrode pounded into to the top of the piston

The ceramic was no where to be seen, it got out somehow, not sure how much (if any) of that damage was the ceramic being chewed up and spit out

I never heard it run but it was supposedly removed for a knock, bearings were suspected but turned out fine

If you know someone with a flexible bore scope it may be worth a look if not drive it and find out what happens

 

[Propflux01]

In the above posting, the major damamge was more than likely caused by the electrode part, not the insulator. It more than likely blew right out the exhaust harmlessly. The big question is what CAUSED the thing to break off in the first place...

 

[kloppilt]

Thanks, guys. The engine doesn't make any noises yet. I'm looking for a replacement nowadays because I am more worried about the 2-3 millimeters of the missing electrode.

It probably was a bad plug to begin with.

The hardest thing to do now is to find a used Accord or Mazda6 with leather interior and stick shift.

 

[Ed]

If it's running smooth and quiet now, it's safe to assume that no damage was done. If a piece of anything was rattling around in the combustion chamber the engine would run like crap. I've heard of stuff getting hung up in the exhaust valve on it's way out but once thats blown out of the way it's of no consequence.
The major cause of broken insulators is overtightening the plug on installation.

 

[Matt_S]

I think that selling it just due to this spark plug issue is a little extreme. If this caused any damage, you would already be seeing it. There are a couple things you can do to ease your mind or verify your suspicion, though.

1 - Find a mechanic with a borescope so you can visually inspect the combustion chamber. If there's any damage, you'll see it there.

2 - Do a compression test. If there's any real damage, it will show as a low compression reading on the affected cylinder.

3 - Monitor oil use. If it doesn't change from what it used to be, you're probably good.

If it was my car, I'd get the compression test. If that showed good, I wouldn't give it a second thought. Why sell a car you like over something that may or may not be a problem without finding out for sure?