98 Merc GM 4.6L Bad miss

Problem has me stumped. Bad miss once car is warmed up. Scan tool says P307...have changed cyl 7 plug and coil boot assy. Problem always comes back to cyl 7. Think my
next step is injector or computer? Is there some other diagnostic isolation I am missing? Ruled out the engine valves or piston because it does not act up until its moving down the road and warm. Any suggestions would be appreciated............jb
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jb@anywhere wrote:

Sticking valve.
More common on the Triton DOHC, but a likely culprit after warm-up.
Maybe a treatment w/ Marvel Mystery Oil & a change to Mobil 1?
If you need an emissions inspection, you're in trouble, otherwise it's probably just a live-with situation on an almost 10-year-old car.
Rob
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jb@anywhere wrote:

Check very close for any moisture in and around the plug well. Any water leaks that dampen the wire but not enough to see without looking real close.
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