What is wrong with this spark plug?



So the real story is I was driving on the freeway and the engine started to sound funny, as if it was running on 3 cylinders. A/F immediately went rich, EGTs fell, and the car lost power. I could not pull over because as soon as this happened I was in a freeway construction zone where all offramps and sides of the freeway were walled off with cement blockades. So I had to keep driving for another 2 miles. During that time, the symptoms resolved.

The next day, it would hesitate on acceleration, but was fine cruising on the freeway. I wonder how it still produced spark well enough to drive, and how much damage that little piece of metal did before it was ejected. I don't see any damage in that square centimeter of viewing area provided by the spark plug hole :)

Ha, nice. I've had a plug almost melt before(a BIG shot of nitrous) but never one look like that. Wonder was caused it. I think a compression test is in order asap, and hopefully it didn't cause any sharp spots in your cylinder that would lead to "hot spots" and have a bad thing happen down the road, or eat some valve.

looks rather normal to me (minus the missing parts)

Can be one of these two, take your pick.

1. Carbon fouled plug, indentified by soft,sooty, black deposits, may indicate a improperly tuned. Check air cleaner, ignition components and engine control system.

2. A physically damaged spark plug servere detontion in that cylinder, If continued detonation can damge the plug and engine also.

Its not a bridged plug with alot of build or extreme gap plug thats been in the engine too long. And its sure aint a oil fouled spark plug(its would be black as your car if it were). Because your plug look pre gap type.

My guess would be number damage plug, the piece broke off where the center soleniod on plug fires.

Originally posted by dalesmitsu
My guess would be number damage plug...

Originally posted by CODE4
Please indicate you have had some level of formal English education.

Has David revoked your grammar nazi privileges yet? :) Oh yes I definitely suspect detonation, even though I'm running low low boost right now. I blame the archaic fuel system I'm running, it is inconsistent at best.

Where's the ground electrode? :scratch :twitch

Could just be a defective plug that had a bad or stressed weld. I don't see any other signs on the plug that would lead me to think detonation.

Like the other guys have said, get a compression test done quick.

When was the last time you've done a tune up?

Originally posted by dalesmitsu
When was the last time you've done a tune up?

I don't remember. I was out of state for a while and so I forgot what exactly the 2g needed done. I just remember the big thing - timing belt in another 35k.

I may have just dropped that sparkie on the ground before I put it in - blame my butterfingers - but it was your standard NGK one range cooler plug. Or maybe I tweaked on it too much with my gap tool to bring it to specs. Anyways now that I think about it the porcelin looks fine, not as if there is any signs of detonation (nor did I ever hear any). I've driven it so much since the plug failed and she seems OK. Per the interwebs 90% of the time the electrode just passes out through the exhaust ports.

i agree w/ zac. do a comp test and if possible, try and source a way to look into the cylinders, perhaps with a lighted fibreoptics scope - see if you see any scaring on the piston top, cylinder walls and if you can, the valve face(s)

Originally posted by 420agreenvilleSC
perhaps with a lighted fibreoptics scope

I wish I had access to such tools :wallbash

Its called a boroscope (iirc) and if you've been driving around and it feels fine the just keep going with it. What ever damage is done by now, hopefully nothing new pops up down the road!

Yup I just put almost 700 miles on her since then, f compression tests. I don't like it as a diagnostic test when my engines sound good, work perfect, continue to have great mileage, and otherwise do not suck in general. Last time I posted compression results on a 4g63, people told me it was time to rebuild the engine or face certain doom. Several years have gone by and that GST is still running fine.