Random "rev limiter" sensation - update - found the problem

[TobyB]

the NGK website has a great comparo feature- and guess what? You replaced a 5k resistance plug with a 1k plug.

What coil boots are you using? Maybe 5k as well?

Because Imma guess you had too much secondary ignition resistance for your setup, and you were getting spark blowout...

t
has had that happen before, but not on an E30... and certainly not COP. But hey, electricity don't care!

[Chilezen]

the NGK website has a great comparo feature- and guess what? You replaced a 5k resistance plug with a 1k plug.

That's handy, I never thought to look for such a thing. Visually, the most obvious difference was the plug gap being smaller (and two electrodes(?)). So I'm assuming less resistance due to smaller gap.
I have no idea what boots, could be OEM for all I know. Are you suggesting I check the resistance on those, just for curiosity sake?

[TobyB]

So inside the spark plug, there's a resistor between the cap and the tip. On what you had before, it was 5k ohms, but on the new ones, it's 1k.

The boots themselves also have resistors in them- the 2 options there are 5k and 1k as well. I treat the boots as I do spark plug wires-
I ignore them until there's an ignition problem, and then I replace 'em.

I do find that the boot resistors burn up- twice, now, I've fixed a spark- loss misfire by replacing boots, and both times, when
I cut the boots apart, the resistors had disintegrated. No idea WHAT boots they were, tho...

t