LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Burned plug wire, misfire?

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Old Jan 12, 2009 | 11:09 PM
  #1  
ascastil's Avatar
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From: Phoenix, AZ
Burned plug wire, misfire?

The answer is obvious. The wire was burned on the header the day of break in, 4000 miles ago. I never replaced it cause it didnt look like it burned thru. Just recently when temps dropped, it seemes to misfire like crazy on cold starts and extremely noticeable at high rpm. The plug wire is on order. My question is this, can a plug wire(that should have been replaced, I know)all of a sudden take a dump and cause my car to run like crap? Keep in mind the car ran awesome until recently. I also put the car onto a lift at work and couldnt see any arching. Shouldnt I be able to see lightning bolts from that wire?
Old Jan 12, 2009 | 11:35 PM
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From: Lima OH
I would repalce the plug wire anyways you should technically be able to see sparks but if you don't that does not rule out the possibility of the wire being the problem. If that doesn't fix the problem check your plugs good luck.
Old Jan 13, 2009 | 12:01 AM
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Damaged wire insulation makes it more susceptible to arcing, corrosion, heat damage, etc. So yes, it very easily could have suddenly gone bad. I also had a wire that was burned, didn't even make it through the first layer of insulation, and it gave me a misfire.
Old Jan 13, 2009 | 12:39 AM
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thanks 93 and green, just to make me feel better while im waiting for my replacement wire in the mail, green you said your wire didnt burn thru the first layer of insulation just like mine, when exactly did it misfire? Mine is more on cold starts and real real bad on high rpm, is this a true sign of a bad wire or should i start looking deeper into the problem, such as bad distributor(accel), even though its 4000 miles old.
Old Jan 13, 2009 | 01:22 AM
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It took a couple weeks after my header install until I got a misfire. I figured I might burn one with the stock routing, so I went right to the wires and found the burned wire.

I have a high RPM misfire right now, and it's also from a bad wire (found it arcing inside the boot, replacing it tomorrow). Wires are the easiest thing to check when you have a misfire, so start there.
Old Jan 13, 2009 | 01:25 AM
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ascastil's Avatar
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Thanks 96, Ill be waitin for my wire, hopefully that works, if not, look for my next post!
Old Jan 23, 2009 | 10:22 AM
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Whats the easiest way to check for a misfire on a wire you found? Start it up, and look at it them while its running right?
Old Jan 23, 2009 | 10:49 AM
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yes that is the easiest way. Do it at night with all the lights off and look under the hood. While its running you might see or even hear the wire arcing. I looked under the hood of my car in the dark when it was running similar to yours and I could hear and see a small flash of light in the engine bay. It also helps you figure out which wire it is.
Old Jan 23, 2009 | 11:49 AM
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Originally Posted by Green96Z
Damaged wire insulation makes it more susceptible to arcing, corrosion, heat damage, etc. So yes, it very easily could have suddenly gone bad. I also had a wire that was burned, didn't even make it through the first layer of insulation, and it gave me a misfire.
what brand of wires was that? im also currently running MSD wires(-1) as are you I see but these things are junk imo. they were alright with my old headers but once I got my new ones it melted the outside plastic on the boot of #8, it didnt even melt all the way through the plastic and was arcing slightly at first but within 2days it got really, really bad even tho it hadn't melted anymore than before. luckily I held onto the stock wires tho so I threw one in and still no problems from it, but I like to have a full set of some quality wires.
Old Jan 23, 2009 | 12:47 PM
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You can't blame the wires for getting burned on the headers. They have to be routed properly.
Old Jan 23, 2009 | 01:12 PM
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ascastil:

What year is the engine/PCM? 96 and 97 can be scanned for misfire count, by individual cylinder.

Info like that should be in your signature.
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