Engine Spark plug wire corona

Barron91lx

Member
Dec 21, 2018
26
3
13
Newton, KS
First of all, thanks to everyone who has helped me work on my car for the last two years.
My 91 5.0 has an unusual problem. Observing the engine running in the dark is a faint light show. Multiple places on the wires are contacting the engine components around them and there is light around every boot. It isn't as bright as a total failure of a plug wire, but it is on every one of them. Interestingly, when I put the coil wire in my hand and move it, the light moves with my fingers. I understand that what I'm seeing is referred to as corona but I don't know why it's happening. I have replaced the wires 3 times in the last year. The advice keeps coming down to new wires. The wires I have on it right now are good ones that I cut to length and they are doing the exact same thing as the others. I grabbed the top of my distributor yesterday and felt a slight jolt where my hand contacted the intake. My distributor is also less than a year old. It's an MSD that I bought new. Could there be something wrong with it? Is it possible for this to occur if the timing is off? I thought it might be the ground so I bought a big ass ground strap that connected to the front ground area and it didn't change. I would try and get it on video but I don't think it's bright enough

Thanks again
 
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My car had a wire or two doing this when I got it. The previous owner had installed new auto parts store wires. I replaced them with Motorcraft wires and the problem went away.

Also it seems there have been reliability issues with MSD distributors and TFI modules as of late so if you have a stock one laying around you might want to give it a try.
 
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My car had a wire or two doing this when I got it. The previous owner had installed new auto parts store wires. I replaced them with Motorcraft wires and the problem went away.

Also it seems there have been reliability issues with MSD distributors and TFI modules as of late so if you have a stock one laying around you might want to give it a try.
Thanks. I'll get my old stock dust out and try it.
 
You have replaced your wires three times, but you haven't said what brand they were/are.
Cheap wires are cheap wires...exhaust heat from a header will make quick work of them if they aren't up to the task. If the rest of these 5.0 guys don't have this eerie glow coming from their engines at night, something with yours isn't right.
I've always used Taylor wires on every car I've ever had, ( and I've had a lot). Despite that, I've never felt comfortable putting my hand on any distributor when the car is running..( I don't know what a " slight jolt" is like, but you get zapped by a MSD amplified coil wire, and you won't describe it as slight) It's one thing for spark to be leaking at the boot, but at the distributor on the other end too points right back to bad plug wires. Do not go through the whole process of replacing a coil or distributor, this is an insulation issue. If anything...put a new cap on the distributor that's on it.