Re:Re:Re:98 Merc GM 4.6L Bad Miss...rest of story

Feb 18, 2007 0 Replies


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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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



Thanks Rob...will check it out. Noticed today that when you are driving and the missing starts, the temp indicator on the digital dash goes from mid range to hot and then immediately returns back to mid temp range. Gets stranger by the minute. This occurs everytime there is a sustained miss more than 10 secs or so???



JB



After a month fo trying different combinations and swaps, the problem turned out to be 2 bad plug coils on the same side. Compression was good in the the Number 7 cyclinder so I ruled out mechanical problems. I won't go in to the embarassing details and costly mistakes I made a long the way, but I learned some good lessions from this one. I appreciate yall's advice on this and thought I would follow up with "the rest of the story"



jb


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