2005 XC90 T5 Spark Plug Problem - Ground is gone!

[oragex]

As above, turn the key to POS II without starting, see if all check lights turn on properly. Also as mentioned, there should be an underlying problem that caused those plugs to snap like such after little miles, lean mixture or a problem with the ignition coils putting wrong tension ? I assume the ignition coils were genuine/Borsch? Perhaps keep an eye see how things go with new parts, good to be attentive at the slightest misfire situation.

[abscate]

I worked on defect analysis in this business a decade ago and the internal electrode failure rate was 10-30% in manufacturing. You definitely see some defect failures in the consumer market place. Most of us other than jimmy won’t see enough spark plugs to see one in retail , though.

That spark plug electrode is down in your catalytic converters getting baked. No worries.

[jimmy57]

The metals in spark plugs, like metals in valves, has changed in the last couple of decades. It used to be more common to see melted away spark plug ground electrodes and center electrodes. Burnt exhaust valves would have a small area on edge and a crack from there towards stem. With the new alloys I have seen spark plugs broken like the ones in the photos and exhaust valves now fail in a way that looks like plate steel cut with an oxy-acetylene torch. The spark plugs with broken electrodes come from vehicles that usually have codes and evidence of lean fuel trim or excessive knock. Overheat can be involved with low coolant or debris blocked radiators. Overboost and use of low octane fuel are regularly seen when the plugs break.

You can still see the melted away failures if the spark plugs are the copper core level plugs. Those spark plugs do not use the "fancy" alloys to give electrodes that have nearly zero erosive wear that the 100,000 mile plugs use.

[cn90]

This is why whenever I replace the spark plugs (let's say every 60K), I throw the old spark plugs in the trunk as spare.
I also keep a spark plug socket/wrench in the trunk.
You never know you need a spark plug in the middle of nowhere, a spark plug with 60K on it is still better than a kaput spark plug.

[oragex]

Note on the side, did such electrode just snapped clear all of a sudden ? That would have caused instant misfire (no combustion) so it should be easy to spot right away. Possible both electrodes failed at once ?