2005 Mercury Mountaineer Power Loss

Tiny
SAMURAIX1984
  • MEMBER
  • 2005 MERCURY MOUNTAINEER
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 179,500 MILES
My wife was driving home this morning and her car lost all of it's power and wouldn't go over 10 mph. The engine has a miss when in neutral that makes the car shake. I attempted to drive the car later when I got home and it is the same issue. It is not running smooth and has no power, I went down the road a couple minutes and turned around. I never made it above 10 mph it just sputters/ misses. What do you think it may be?
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Wednesday, May 6th, 2015 AT 3:05 PM

5 Replies

Tiny
CARADIODOC
  • EXPERT
Hoe long since it had a tune-up? Worn spark plugs are the best suspect.
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Wednesday, May 6th, 2015 AT 5:43 PM
Tiny
SAMURAIX1984
  • MEMBER
New plugs a few weeks ago.
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Wednesday, May 6th, 2015 AT 6:34 PM
Tiny
CARADIODOC
  • EXPERT
The next thing is to have the diagnostic fault codes read and recorded. Those do not tell you parts are bad or need to be replaced. They indicate the circuit or system that needs further diagnosis. They can also tell you which cylinders are misfiring.
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Wednesday, May 6th, 2015 AT 8:00 PM
Tiny
SAMURAIX1984
  • MEMBER
I had that done and all it said was cylinder 8 misfire, I put a new plug wire coil on it and that seemed to do the trick, then this happened.
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Thursday, May 7th, 2015 AT 2:38 PM
Tiny
CARADIODOC
  • EXPERT
I'm not understanding the chain of events. You're saying there was a misfire, there was a diagnostic fault code referring to cylinder 8 misfiring, you replaced the spark plug and wire, the problem was gone, then this new problem of failing to accelerate along with another misfire has occurred. Is that right? If so, you have to start over with the same diagnostic steps. Logically you would want to replace all of the spark plugs and wires. Next is to erase the previous fault codes if they weren't already, then see if new codes set.

If the previous codes weren't erased, the simple fact that they're in memory can cause the Engine Computer to suspend some self tests that rely, for comparison, on anything it thinks it can't trust because of those codes. Once the old codes are erased, the rest of the tests resume, and that's when new problems will be detected.

Also, your engine uses the scary "throttle-by-wire" system that put Toyota in the news a few years ago. If that system shuts down, the throttle won't respond when you press the accelerator. That shutdown can occur because of a problem or as the result of some other problem. Either way, that is something you want a professional to look at.
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Thursday, May 7th, 2015 AT 8:29 PM

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