Question about plug top ignition coils.

It depends on the failure mode. They shouldn't need replacing any more often than a conventional coil.

Bet VW wish that was true.

aren't the only ones. Nissan have had troubles with V6 coilpacks, mainly reported on USA Maxima. Coils don't like being in hot places. Coils don't like vibration. Cylinder head is hottest most vibratory place you can find on the outside of the engine.

Cut the winding gauge to save 1p/coil and you have a sure fire recipe for trouble. Cut the encapsulation by a few grams/coil and you have a sure fire recipe for trouble. When you are saving 4 or 6p per engine it's far more tempting to make that saving than the 1p saved on a single coil engine.

Only a mug would pay someone to replace a good working set of coil packs for new ones that may be from a batch that have been made after or during a cost reduction program.

Yes, some more than others (Saabs and GM seem bad, IMHE)

The problem is heat. "Traditional" coils were oil cooled (and had inefficiet core designs), then we switched to larger looped cores and good airflow around them. A few cars didn't get this airflow right and suffered accordingly. if you make any electronic compoenent dependent on insulation, then you cook it, you'll get failures.

It happens that Mike G formulated :

Just like normal coils they can break down under pressure. The mode of breakdown can be anywhere between complete failure and reduced performance. Unlike a normal coil they often work under hot conditions which can add to their liklehood of failure.

If a problem is suspected, then is worthwhile having a known good working coil pack around to use as a test substitute.

Thanks all. As I suspected then. Just more advice from someone who doesn't really know if it is true or not. Probably simply repeating what he was told by someone who was equally uninformed. Mike.