Citroen C4 Cactus Ignition Coils

Single coils run R300 to R2,400 through our network depending on the engine and the brand, and a full set of four for a C3 or Xsara generally comes in under R3,000 for OEM-specification aftermarket units. Buying the set is usually the right call on a car past 90,000 km, because the remaining coils have taken the same heat and voltage stress as the one that just failed.

A rough idle, the engine warning light, and a misfire code pointing at one specific cylinder. The characteristic feel is an engine tripping over itself at low revs that smooths out on the open road, because at higher speeds there is less time for the misfire to be noticeable and the coil is under less relative strain. Consumption climbing is the other reliable clue, since unburnt fuel is being pumped straight out.

Around R500 to R2,600 fitted per coil at an independent workshop, parts and labour together. Doing all four on a four-cylinder petrol together with a new set of spark plugs comes to R2,350 to R4,950, and we recommend that combination rather than a single coil almost every time — the plugs are what stressed the coil, and replacing one without the other leaves the cause in place.

Only as far as the nearest workshop. A dead coil means that cylinder's fuel is not burning, so raw petrol goes down the exhaust and ignites inside the catalytic converter, which melts the substrate within a few hundred kilometres. That is the calculation: a coil is around R600, and a catalytic converter it destroyed is in the region of R15,000. There is no version of driving on a known misfire that saves money.

90,000 to 120,000 km on the C2, C3 and Xsara petrols is typical. Short-trip driving shortens it, because the coil spends proportionally more of its life at the high stress of cold starting. Old spark plugs shorten it dramatically, for the reason above. Fit plugs and coils as a set at the interval and both last as they should; skip the plugs and you will be back for coils well before the mileage suggests.