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4.6 Keeps shorting/melting/burning coil packs

Old 03-18-2016, 02:50 AM
  #1  
latinheat1018
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Default 4.6 Keeps shorting/melting/burning coil packs

My 4.6 just started burning/melting/shorting a specific coil pack. The cylinder at the very front on the passenger side.
I mentioned it to a trustworthy and experienced mechanic and he said that it's the computer. And that it's a fairly common problem in these cars.
I cannot drive the car to him so I'm trying to fix it myself.
After buying a new computer and having it reprogrammed. Is it necessary to change all the coil packs and spark plugs as well?
Has anyone had similar problems here? if so, how did you fix it?

Thank you for your help
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Old 03-18-2016, 07:12 AM
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fastbackford351
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I hadn't heard of that happening before but that doesn't mean much. Your plugs and coils will be ok with your new unit.
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Old 03-18-2016, 07:15 AM
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dawson1112
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It could be a bad coil driver in the PCM , but it could also be a short someplace in the wires that go to that coil. Once you find the problem there will be no need to replace all of them.
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Old 03-18-2016, 07:50 AM
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proeagles
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Do you have a "tune" on your car?
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Old 03-18-2016, 08:56 AM
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Drastang
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I would start by getting a coil/voltage tester they are cheap and start testing lines. sounds to me like you might have it making surface contact.
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Old 03-18-2016, 02:47 PM
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jwog666
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here is a thread i found describing a wire chaffing issue that caused a concern like yours
http://www.allfordmustangs.com/forum...runing-up.html
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Old 03-18-2016, 07:04 PM
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WJL
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The coils are ground side switched, so if one of the ECU controlled ground wires on the coil is grounded the coil will try to constantly fire resulting in failure.

Very simple check, check for continuity between the ground wire for the coil to body ground, if you have continuity the wire is shorted to ground and this would be the cause.

If you don't have continuity, check the coil wiring harness, could be shorted to another wire.
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Old 03-18-2016, 11:47 PM
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jwog666
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a coil will only fire after it is grounded for a period of time, (dwell), and then the ground is removed, (opened), this causes a colapse of the magnetic field in the coil of wire and induces a voltage, (spark), in the secondary side of the ignition,(spark plug). if the coil is shorted to ground, it will not fire at all. a short to ground on the ground side of the coil will result in a dead miss on that cylinder and a direct short to ground,causing the coil to melt. it at no time will fire, (spark), at all.

Last edited by jwog666; 03-18-2016 at 11:50 PM.
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Old 03-19-2016, 12:36 AM
  #9  
latinheat1018
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Thank you for all your responses. I appreciate all the input. I work all weekend long so I won't get a chance to play with it. I'll track the wires back and see if i find anything. I'll post what I find.
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Old 03-19-2016, 11:34 AM
  #10  
WJL
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Agreed much better explanation, the point i was trying to make is if in fact the coil is grounded it will burn up and fail
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