On 01/12/2016 at 0:32 AM, Tdci-Peter said:

That comment puts my bull-dung detector into amber alert. I am not sure what "blown wiring" is, in this context. It is more likely that a wiring fault was the original cause, maybe there was nothing wrong with the coil pack. The 12v feed to the coil pack has been known to develop intermittent faults. It goes through various connectors & splices.

But to be fair to the garage, replacing the coil pack is quicker, and hence at garage labour rates cheaper, than investigating the wiring, so they may had little choice than do it that way round.

The error codes that must be being generated might give some clues. The more, the better. Is it one cylinder, or all, or maybe some other sensor is giving an intermittent error.

Because the coil pack creates a high voltage (enough for a spark to jump in essentially high pressure fuel and air mix), it is susceptable to insulation breakdown and failure of electronic components (all enclosed in hard resin by the looks of things). Wouldn't have thought it would have blown wiring (would have blown the fuse first...). Had a look at mine, no obvious external damage, cracks, etc. It has what appears to be a date "09/10/12". 12 October 2009 kind of matches previous dates i've seen around my engine bay (2010 car), but concerning more is if the date is as it is read, meaning that it was replaced in 2012 also... My car did come originally from Jersey so has been around - unfavourable - coastal weather.

I’m having a similar problem to this, car was misfiring & juddering, Forscan said misfire on cylinder 4 so all 4 plugs were changed car run some what better then after 5 minutes went back. Struggles pulling under acceleration & the Juddering is a nightmare. I’ll be replacing the coil packs too after reading this! Thanks guys for an in depth interesting read!