I've got a 2003 Kia Rio (4 cyl) that started shuddering on me yesterday. When I got home I found that the cylinder 3 spark plug wire had gone bad. Sparks were coming out the side at an apparent insolation leak rather than out the bottom to the spark plugs. I replaced wire 3 with an old one I had lying around. Took it for a test drive and all seemed fine.
Now one day later, severe shuddering starts up again. Its the same failure but in the cylinder 1 wire! Sparks coming out the side. Replaced it and again things seem okay.
Is this just a coincidence that two wires would go out independently 2 days apart? They're from the same original set and are 20k miles and 3 years old.
Any ideas what is the likely cause? Coincidence or something more sinister (i.e. expensive)?