I've got a MK2 Fiat Punto Sporting Year 2000 Model which I've had since new - only has around 30,000 miles on the clock as I mainly use it to drive to the train station or local shopping with only occasional trips up the M1 for about 20 miles each way.

All of a sudden the car seems to be misfiring. I changed the HT Leads about 18 months ago - previous to that it was the original leads - Back then I noticed that after 2 days of constant rain the car was very jerky when driving. New leads seem to solve the problem.

However now 18 months later I am getting a misfire. The Spark plugs are only 2 years old but I had some new ones so I changed them for the new ones today and the misfire has improved - there is less shaking of the engine but it's still misfiring (although I have driven anywhere yet today since changing to new spark plugs)

Is it likely to be the 18 month old leads? Coil pack or something else?

Below is a photo of the old spark plugs if that helps at all. They're laid out in order they were removed - with the left one closest to the driver's side of the car and the right one closest to where the car battery is.

I am wondering if it is the leads that are the problem, could the reason things have improved simply be me disconnecting and reconnecting the wires, rather then the fact I happened to have brand new spark plugs in there.

BTW I don't have any signs of a head gasket leak that I can see, there's no milky mark on the dip stick or the top of the oil cover. No signs of car overheating, etc.