4.6L Continental missing under load

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  #1  
Old 03-02-09, 01:25 PM
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4.6L Continental missing under load

My mom's 99 lincoln continental 70K miles is missing under load at around 2500 rpm. If I back off the throttle, so it is not under as much load, I can get it to 3500rpm before it starts missing. It is almost acting like it its hitting a rev limiter. I replaced the coils and plugs on cylinders 1 and 4, and the idle air control valve about 2 months ago.

The codes are
Small vacuum leak, evap system (has had this for about a year)
Cylinder 4 misfire
Cylinder 5 misfire

What could be causing this? In my previous experiences when its a bad coil, it will miss at the lower rpm's too.

Thanks
 
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  #2  
Old 03-02-09, 02:15 PM
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First pull the coils on 4 and 5 and see if there's oil or water in the hole where they reside.........If oil, you need a valve cover gasket or you can put all the coils in the world in there and the oil will ruin them all......
Question........What BRAND of plugs did you put in???? (PLEASE don't say Bosch)
 
  #3  
Old 03-02-09, 02:26 PM
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I used autozone coils and motorcraft platinum plugs.

No, no bosch. I made that mistake with my grand am about 5 years ago. Used bosch platinum plugs, ran great for about a month, then the little tips fell out of two of the plugs. Hope they ended up in the oil filter. Never found them.

How does the oil ruin the coil? Does it degrade the rubber boot?
 
  #4  
Old 03-02-09, 05:22 PM
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You got it........swells the rubber till it splits and the coil arcs out to the sides of the tube
 
  #5  
Old 03-06-09, 10:38 AM
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Thanks Wrench,

I replaced the coils and plugs on cylinders 4 and 5, and but that didn't help. I also replaced the fuel filter, just in case, but that didn't do anything either. I cleared the codes, and have driven about 60 miles in about 5 trips, but the ses light won't come on. It still is running poorly.

It bogs down when the throttle is pushed down. It runs up to about half throttle, then bogs down, at around 2500rpm.
If I push on the gas to 3/4 or WOT, it just bogs down, if I back off to about 1/3 throttle, it picks back up.

Im stumped
 
  #6  
Old 03-06-09, 01:16 PM
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if its bogging down it sounds like a fuel problem or maybe an exhuast restriction might be time for a fuel pressure test while driving and most exhuast shops can do a back pressure test on the exhuast system.
 
  #7  
Old 03-06-09, 04:54 PM
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it could possibly be the mass air flow sensor,try unplugging it and driving,it will set the ses light but it will run with it unplugged
 
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