Exploding spark plug

I pulled the 99 spec Boxster out of hibernation a couple of weeks ago for a day of testing at Lime Rock. The car was missing badly and the fault codes said a misfire on #1. I suspected the coil pack and I didn't have any spares so I packed up and went home. Since I was changing one, I decided to change all the packs and do plugs and tubes while I was at it. I'm glad I did because the plug in #1 has nothing inside it. No anode, no insulator, no nothing. I found some fine shavings in the tube with a magnetic probe but the anode should be nickel I thought. Maybe other plug innards? I hooked up a piece of clear fuel line to the shop vac and heard a few pieces come out of the tube but nothing out of the cylinder. Aside from taking it to the shop for a look with the boroscope, any ideas on how to determine if anything remains and to get it out without removing the heads?

Thanks,

Scott

Quote
scott in pa
I pulled the 99 spec Boxster out of hibernation a couple of weeks ago for a day of testing at Lime Rock. The car was missing badly and the fault codes said a misfire on #1. I suspected the coil pack and I didn't have any spares so I packed up and went home. Since I was changing one, I decided to change all the packs and do plugs and tubes while I was at it. I'm glad I did because the plug in #1 has nothing inside it. No anode, no insulator, no nothing. I found some fine shavings in the tube with a magnetic probe but the anode should be nickel I thought. Maybe other plug innards? I hooked up a piece of clear fuel line to the shop vac and heard a few pieces come out of the tube but nothing out of the cylinder. Aside from taking it to the shop for a look with the boroscope, any ideas on how to determine if anything remains and to get it out without removing the heads?

Thanks,

Scott

Too bad you did not shop vac the cylinder with a clean vac. It is so important to note in these cases how much material one gets. From this he can estimate how much is left in the cylinder.

Without a borescope of the cylinder's surfaces or removing the head you can't know you got everything.

With the scope or the head removed you can check for a damaged valve or valve seat. A piece of the plug can get caught and put a nick in the seat or valve lip and this can lead to a burned valve.

The engine will miss and if it does it will need the head removed and the valve or valves replaced and the seats repaired.

You can also check for a piece of plug embedded in the piston crown or combustion chamber. In either location the piece will likely cause preignition

Remove the fuel pump fuse. Remove all plugs. Rig up a hose to the vac to the plug hole of the cylinder. Have a helper crank the engine. This will remove any loose pieces still in the engine though since you drove the car some with the fragmented plug what you didn't get with the vac probably went out the exhaust port.

Then if you're feeling lucky button everything up and fire up the engine.

Otherwise borescope the thing or remove the head.

Thanks Marc,

Yes, I know, I should have cleaned out the vac before I started. I had a short window of free time and curiosity won out over common sense. The engine was just rebuilt last year at considerable cost so I want to proceed carefully.. I ordered a relatively cheap boroscope, should be here by Monday. Had to drop out of the Lime Rock race this weekend because of this and time constraints, Now I just need to get it back in shape for the Glen at the end of May.

While waiting for my scope, I disassembled one of the other plugs yesterday. I'm not really worried about the ceramic but that's a big chunk of nickel and it is indeed magnetic. I guess I wasn't paying attention that day in Chemistry.