Due to a feeling of poor performance, skipping a beat and just feeling like it wasn’t firing on all cylinders – actually – thought I’d change the plugs. For some reason it’s one of the things I should have at least looked at, but never bothered with.
At £16 for a set of originals, it’s cheap worthwhile maintenance. The only annoyance is that an extra long spark socket had to be purchased as the two I had from sets were the wrong size, still just a couple of quid extra. Fortunately the HT leads were all in good condition, just a quick clean with a wire brush, some WD-40 and ready to be refitted. In all the job took about 30mins and the car is running much smoother and has more power.
Taking a look at the old plugs is important as it yields useful info about what’s happening in the engine. These plugs, laid out in the order they were removed, show cylinder 3 was suffering from a bad connection to the HT lead. The rusting of the protruding connector likely happened due to water getting behind the HT lead/engine block seal and resultant arcing. Unfortunately the design on the engine block funnels water to cylinder 2 & 3 when the engine is being cleaned. The NGK plugs here are performance, not going by the ‘R’ which might furtively suggest ‘race’ but that there are two electrodes to the side. The standard is one over the top, this alternative configuration can be better for increasing life of the plug by providing more ignition surface. I consider it pointless, as there are other things that’ll kill the spark plugs, and the diagnostic info from checking them is more useful for addressing other issues (oil burning, fuel mixture, etc.).
Anywhere from £60 to over £100 done at a garage, sorted at home for £16.