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758 Posts
You said you replaced the plugs, but didn't mention the coil and plug wires. If they've never been replaced, the coil likely has all sorts of cracks in its exterior case (ours did). Original plug wires ought to be replaced as well, in my opinion, due to age and miles. They may "look good" on the outside, but that might just be hiding interior deterioration due to years of heat and vibration.
