IGNITION COIL FAILURE

A poor idling quality and below-par performance when driving will be evident when this fault is present. In the early stages the engine management warning light may not be illuminated – but if the trouble is not fixed and left to its own devices, almost certainly the light will be on, and the system will register a code relating to ‘cylinder misfire’.

Usually it won’t be necessary to use a diagnostic tool to find the fault… Remove the ignition coils individually and check

for signs of arcing – you will see where the spark has been escaping and not finding its way to the cylinder concerned.

Edward says that it’s worth noting that many times when he has seen this fault the vehicles concerned were poorly serviced and the spark plugs were well overdue for replacement. Worn-out spark plugs place additional strain on the coils – although he adds that he can’t say 100% that failure is always due to a lackof-maintenance issue.

He advises using quality components when replacing the coils, and ideally fitting new units. Again, though, installing good-condition secondhand coils can be a cost-effective option.