99 ML 320 with just over 200K miles. Had local indie change spark plugs and all plug wires at around 110K. I plan to do it myself this time. I plan to get the OEM plugs and wires from Phil.

Do most of you guys replace all 12 wires, or just the ones that are worn out / defective?

And how specifically do you tell if a plug wire is defective. I think you measure resistance, but would appreciate detailed instructions.

Thanks.

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I replaced mine at about 65,000 mi and it's probably best to replace all the wires. The entire job is not too difficult, but you do have to be careful and patient when removing the wires from the plugs (they can be tough!). If you do a bit of research on this forum or others, you can find some very good info on the whole procedure. Good Luck!

High mileage spark pulgs PUT extra stress on the wires & that causes them to "LEAK".

Replace them ALL. Use Bosch as they are OE!

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Thanks everyone. I'll plan to replace them all.

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