Spark Plug Resistor Cap as a source of misfiring, various versions with or without adaptor cone.

Misfiring can be caused by defective or poorly seated Spark Plug Resistor Caps. HT Leads and plugs should therefore be checked first in the event of such problems and replaced if necessary. There are various Spark Plug Resistor Caps to choose from, which can be used with or without the spark plug adaptor cone, depending on the version.

Conclusion: Should be replaced with every major engine overhaul and belongs in the Glovebox as a spare part.