We recently found out by pure coincidence that our HP had the top spark plug cap (with the green marker on it) dangling loose for at least several thousand kilometers (at least since the last time if was put on the bridge at the dealer). I asked the dealer to remove both plugs so we could have a look. The top one (the disconnected one) was coated in black carbon and did not look good. The bottom one (that had to do all the igniting on its own), didn't look to good either, but instead had brownish muck coated on it. I did not yet get the chance to compare them to the ones on the unaffected rotor, but I will.
All the plugs are going to be replaced of course, and I asked the dealer to inspect the cat, I can imagine there may have been misfirings that put unburned fuel into the cat. He is also going to check the ecu log for any error-reports.
Does anyone know what could be the effect of running with one less spark plug for an extended period, and how to recover from that?

 

it's not the end of the world. dirty plugs can easily be cleaned (and are not worth the $15 or $20 per pop for a new one considering that they're so early into their duty cycle in the engine, being irridium), and catalysts function on their being left over air and fuel from combustion (it's there to clean it all up). even if it's fouled a little, taking your car out for a ripping good drive would help out with that.

your engine is most probably fine. your spark plugs are also fine. your cat, well, even that too is alright, and you'd know if you failed an emissions test miserably whether or not it's been ruined (although i'm still not sure you can ruin it by giving it a little more fuel than it's used to).

being that the stray wire didn't short anything out or kill anyone, i think you're already 'recovered'.

 

We may have killed several without us knowing about it. Those high voltage lightning bolts can be very dangerous.
I suspected it would not be the end of the world, but was wondering if the continuous suboptimal combustion might foul things other than the plugs, or damage the cat. Probably nothing a good hard drive can't burn away then... :D

 

Are iridium plugs only $15 in the US??!!

 

last box of 4 iridium plugs cost me about $75 or so for all four. So $15 is about right.

 

You bought plugs for the 8? Where did you buy them?

Last time I looked, no one had the NGK's the 8 uses other than the Mazda dealers and they were all charging a premium.

 

this happened to my car too, hard to imagine how a plug wire came loose, maybe it was when the cops were putting that gps tracker on my car, anyway removed the gps, and the dealer had to replace the plug and plug wire.

 

Bump: Where did you find them for less than $120? And was it two of the 7's and two of the 9's? Or are you buying a box (4) of the 7's and another box (4) of the 9's?