Current mileage is 97,558. I bought in February and don't know if plugs have been replaced. I aim to go ahead and do it, but really, even with the possible mileage on them, does it seem likely it would suddenly skip on half the cylinders, with 3 plugs going out at once?

Good idea about the ground on the head cover. Any tips on exactly where to look for it? Front of head, middle outside, back, etc.? Anything that might help is appreciated!

Anyone know if vacuum leak would signal a misfire DTC, if the plug itself is still firing? Or does a misfire code mean that the plug is absolutely not firing? Knowing this might differentiate the problem between vacuum or ignition system....

Thanks for the brainpower help!

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2009 X5 3.0
2001 X5 4.4 - Sold