Occasional intermittent 'fluff' - (misfire)

[pundit]

My engine (M30) has the occasional slight misfire. Noticeable at idle and low revs. Nothing appears obvious whilst driving. I've recently fixed a couple of vacuum leaks and cleaned the idle control valve and replaced the spark plugs (Bosch W8LCR). It appears as the typical type exhaust 'fluff' with the 'suck back' hiccup every few seconds. Little like a leaky exhaust valve, however it will then often disappear altogether. Valves recently set at a 'moderately loose' 12 thou (cold). The distributor cap and rotor were fine and I'm beginning to suspect the plug leads are beginning to breakdown as it appears it maybe be high tension arcing between adjacent plugs leads which is causing the misfire, probably all happening inside the lead conduit I suspect.