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I've replaced the coil pack and fitted new spark plugs. However, the salesman, while handing me the plugs, accidentally dropped two of them on his table. I remember them dropping from about 2 inches above the table. They were still in their boxes and hit the table horizontally. I carefully inspected them twice before handing the money, and the insulator (both the visible part of the core and the stem) seemed fine with no visible cracks, the gaps were also right, so i bought them.

I've installed them, and after driving around for about 3 days, the car is idling fine and acting like it isn't misfiring under load (previous coils and sparks were causing a minor misfire on the 1st cylinder and this made the car noticeably hesitate under load, even though it still idled fine), both on a cold engine and a hot engine.

Am i worrying for nothing, or would i better change all sparkplugs again?

  • I've tried dropping the old spark plugs (bad spark plugs, OEM no longer sells them) from the same height on my table while inside their boxes, and i'm positively certain that no cracks appeared on the insulator anywhere and the gap didn't change. – Al_ Jan 14 at 11:03
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Leave them in - sounds like they are fine.

Usually if they land wrong, the insulator is cracked or the earth terminal bent, but you did not find anything like that.

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  • It basically landed on the hexagonal nut. I'm worried the shock cracked the insulator inside there if the nut didn't shield it somehow. – Al_ Jan 13 at 17:22
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It doesn't matter whether you've dropped a spark plug or not,

Check the gap with a gauge before installing them in the vehicle!

While 99.9% of spark plugs come properly pre-gapped, it is wise to take an extra second or two to check the gap for each plug against the recommended width with a spark plug gapping gauge.

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  Variety of common spark plug gapping gauges

It's just simply a good habit to get into and becomes more important when the spark plugs have been mishandled.

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    Gap was 0.9mm on all plugs like supposed to. Engine is behaving perfectly by now. Prior to this service it suffered serious hesitations especially while driving uphill – Al_ Jan 13 at 20:08

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