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I took my VW Golf MK5 2005 (130,000 miles) to have a full service the other week which included changing all 4 spark plugs. Whilst driving home the engine management light came on and I lost some power in the car.

I took my OBD reader which showed there was a cylinder 4 misfire. I took it back to the garage the next day and they tested and told me it was the ignition coil for that cylinder. They informed me that the coils can be quite delicate and don't always liked being moved. To be fair to them they only charged for the new coil.

3 days later after moderate driving the same situation occurred and I lost approximately 25% power again. The OBD reader showed a cylinder 3 misfire this time.

My question is will this most likely be the ignition coil again for the 3rd cylinder and is this the fault of the garage who did the service? If it is the coil then I am tempted to just change it myself.

  • By 'Coil Pack', do you mean individual ignition coils or literally a coil pack, where the pack contains a coil for each cylinder, hence replacing the pack replaces all coils? – HandyHowie Mar 17 at 7:51
  • @HandyHowie Thanks for the clarification - I mean the individual ignition coil like this eurocarparts.com/ignition-coil – AWGIS Mar 17 at 8:37
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It very well could be. My experience is that these things fail in clusters. The easy way to check is to swap 3 with 4 and see if the misfire moves to 4. At this point you should be able to get a new one at an auto parts store and replace it yourself.

Alternatively, you could go back and have the dealer look at it again. They might do it without labor charges again but I'm going to suggest you replace all 3 of the remaining old ones.

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  • Someone mentioned to me that swapping them is not advisable as you may break the good one if the problem is with your circuit. Is this something to be concerned about? – AWGIS Mar 17 at 9:06
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    I've never heard of that or experienced it. The bad ones usually have failed due to cracks in the coil windings or breaks in the enclosure allowing moisture to enter and cause shorts. It's the hot/cold cycles that these experience that causes the issue and the new one is not susceptable yet. Remember that your old ones are 15 years old and have thermal cycled 100s if not 1000s of times. – jwh20 Mar 17 at 10:40
  • Thanks I have tested and it seems to be the issue. I have now ordered 3 new ignition coils. @jwh20 is it important to apply silicon dielectric grease to the ignition coils? – AWGIS Mar 17 at 13:21
  • If the instructions call for it, yes. Otherwise I would avoid it myself. – jwh20 Mar 17 at 15:21

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