The unstated issue, of course:
...causing general misfiring, jerkiness, stalling, severe lack of power particularly under load (just when you need it!) and massive fuel waste which can then knock on to overheating and catalyser damage.
Just fallen prey to that. Thought I'd clean the engine area up given the huge amount of salt the car's been battering through over the last 4 months.
didn't like that one little bit. Had to replace two of them (outer pair), and might have to do the inner pair later. For now, WD40 seems to have sorted them. (Good thing, because some previous cack handed mech has rounded the torx on one of the inner bolts).
Luckily they're not too expensive (£24 or so each for decent-enough Beru units from GSF, plus £1.50 for a fresh sparkplug (mine were badly fouled and overdue for a change anyway), plus VAT), but doing the change can be a nightmare unless you have quite a good toolkit.
Found e.g. I didn't have a proper holder for small torx bits (had to wodge a little blu-tack into a 1/4" socket) and that the gunk holding the fouled plugs into their holes is actually stronger than whatever holds the rubbery suction cup thing into the spark plug socket... cue making up improvised tweezers from barbecue skewers.
Plus the torx for no.3 cylinder's
is partly obscured by some mystery, possibly pointless plastic moulded thing on the inlet manifold... probably why that one got rounded, it's almost impossible to get a bit to sit straight in it. Whoever designed this engine layout needs to be taken away by the men in green coats.
Also when the
fail they leave behind nasty melted-plastic residue that would only shift out of the plug recess bore with use of white spirit, a wire wool bottle brush and much scrubbing. Flamin' Nora. Could've left it, but don't want to risk it somehow affecting the new ones.