Ignition cable replacement

[Metroplex]

Quick question, when should one replace ignition cables to the spark plugs? Is there a general mileage/age rule? Mine are probably originals. (92)

 

[almostclueless]

Specifically when they have cracks or burn spots on their insulation or other damage, or when they have resistance beyond the factory spec (factory manual should specify), or a diagnostic at a shop indicates so.


If I buy a vehicle that isn't brand new, I replace the plug wires soon with high quality, like the motorcraft wires I bought for my 98.