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Can bad coil packs make new problems?


Old 07-07-2005, 02:50 PM
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Location: Denver, CO.
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Can bad coil packs make new problems?

I own a 2003 Scab , 5.4, 4x4, and have not had a lick of trouble with it. I talked my father into buying a 2005 Screw 5.4, 4x4. The truck had a bad misfire with 3,800 miles on it. The dealer replaced /repaired the coil on plug system and said that would be the end of the problem. My father went on a road trip and the misfire started again in the middle of the desert on the way to Las Vegas. He had to drive it about 70 miles with the misfire. A dealer in Vegas repaired the COP's again. I just wonder if any other issues will surface due to the fact that the truck was driven with the misfire. Any possible damage to sensors or catalytic convertors or anything for that matter. He is taking it to a local dealer today for an inspection, anything i can tell him to watch out for or ask about would be appreciated. Thanks.

I posted this on the 05' forum but no luck with any answers, thanks. I have searched and no one seems to address any future consequenses of the bad packs.
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Old 07-07-2005, 11:47 PM
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Location: Fort Worth, TX
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A misfire due to a bad coil shouldn't cause any other problems. It could have possibly fouled the o2 sensors, but more than likely would have set a code if that were the case. If it did start running poorly, o2 sensors would be were I would start. Other than that, as far as long-term irreversible damage, I wouldn't think so.
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Old 07-07-2005, 11:50 PM
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Join Date: Jul 2003
Location: canada
Posts: 8
Hey dude, I don't know much about the coil on plug system, but I have seen arcing form plug boot to head that can be hard to find. As far as possible damage, you do run the risk of a cat converter meltdown. Every time the engine misfires it dumps raw fuel mixture ito the exhaust which can burn up the ceramic in the cat. And I do speak from experience.

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Old 07-08-2005, 02:12 PM
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Thanks for the info you two, my dad did say that the truck was spitting white smoke while it was misfiring. The dealer has it now and is doing an inspection, I will let my dad know about the other possible issues.

Thanks again
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Old 07-08-2005, 06:16 PM
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Join Date: Jul 2004
Location: Easton, Pa.
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Missfire in these engine manegemant systems is quite complex.
There are a number of reasons why it can happen either as a single fault or in combination with another fault or one fault causing another.
This is why there is such difficulty in running down a missfire as compaired to an older distributor/cap/wire engine.
1. Plugs.
2. Coils.
3 Their boots.
4. Fuel injector.
5. Fuel.
6. EGR operation.
7. Wireing.
8. Water or coolant leak into the plug area.
9. Valve cover seal around the plug area.
Any single or combination of these can cause it.
Then how the computer detects and set the code/turns the CEL lamp on it is another involved explaination.

The more the person doing the job understands, the quicker the problem is solved. There is a great tendency to just stop at the first thing that seems to clear the fault, only to have it return.
Example: a bad plug can take out a new coil in a short time by allowing the spark to punch through the boot when it can't fire accross the plug gap.
People who swap coils often end up waisting more coils than the original bad coil until they get to the end and finally swap out the bad one being moved around. They end up with a bad plug that took out more than one coil until both are out of the system by the swap process.

There is a judgement call on some of this that can create some PR trouble by doing the extra work, to be sure, then have the customer ask way all the extra work and parts.
But that's the world we live in.
Knowledge is power.
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