some findings on a customer this weekend...

These would have surely led to misfirses, and ultimately a damaged engine. The spark plug recall was supposedly done. I always re-check to make sure the right plug is used, and they are tight enough.

3 problems. First problem, they are bosch platinum. They have proven they can not be trusted to stay together.

#2 cylinder plug was loose, had combustion blowby. Traces of burning on the coil. This will surely lead to a misfire, and a fried cylinder.

#3 cyl had a cut plug tube seal, and was pooling oil in the spark plug well. This will short out the coil and cause a misfire.

Plugs, 1-2-3-4:

 

Hmmmm, interesting...
I just had a CEL p0304 come back on my car after 6 months... First time it appeared, I changed plugs with NGK's, gapped them properly, and torqued 'em down to spec and the CEL stayed away... The OEM's didn't look that bad or oil covered...

Just curious as to what my next step should be now...
I can hear it misfiring through the Invidia at idle...

 

so what would be the best plug for the car

 

NGK is your friend.

https://www.s2ki.com/forums/index.php?showtopic=458938

 

I'd bet the plug recall was done, then a zealous owner thought they where improving things by switching to the Bosch's.

Some things are best left alone

 

For NA, or SC on stock boost, OEM plugs for sure.