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Discussion Starter #1
87 5.0 21k miles.This thing has melted the boots on 3 sets of wires.I ordered a set of Taylor 2000 degree ceramic boots and put them on 2 days ago. Now these are arking down the plugs on passenger side. They are seated good, new Motorcraft copper plugs set at .44. What would cause this problem. I love my ride but about ready to get rid of it. Any help would be appreciated. Thanks
 

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I could be wrong, but an improper air/fuel ratio can cause elevated exhaust temps. You say it only has 21k on it so I am guessing a build or rebuild.
Are the wires touching the exhaust?

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84 Bronco, 351w, c6, custom doubler, np208, 5.13’s, TTB44, 9”, locked f/r
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Stock manifolds or headers?
What is the timing set at?
Lean fuel mixture makes a lot of heat too, have good fuel pressure and a new fuel filter?
 

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It is a bought rebuild 3.5 years ago, out of warranty now. Stock manifolds. New fuel pressure regulator,high pressure pump,filter, no wires touching. I am concerned with the arcing with new plugs and wires. timing set at 10 bdtc.
 

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84 Bronco, 351w, c6, custom doubler, np208, 5.13’s, TTB44, 9”, locked f/r
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Were they arcing as soon as you put them on, or did they bake for a while and then get crusty and start arcing? It’s weird to me that they are getting that hot even through header wrap or fancy boots. How hot do the manifolds get, they don’t start glowing or anything crazy like that do they? Maybe plugged cat or broken and plugged up muffler???
 

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Yo swafford,

Spark Plug Wire Routing & Firing Order TSB 94-04-10 for 87-93 5.0 & 94-96 5.0 & all 5.8 - engine miss, spark knock, buck/jerk, surge and other driveability concerns;
● MIESK5 NOTE; The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark plug wires are routed next to each other at the separation bracket, an induction crossfire condition can occur.

See Routing @

Diagram for 5.0 in 87-90 Bronco, E 150, E 250, F 150, F 250; engine miss, spark knock in TSB 94-4-14
Source: by Ford via Chilton
 

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Discussion Starter #9
Were they arcing as soon as you put them on, or did they bake for a while and then get crusty and start arcing? It’s weird to me that they are getting that hot even through header wrap or fancy boots. How hot do the manifolds get, they don’t start glowing or anything crazy like that do they? Maybe plugged cat or broken and plugged up muffler???
no cat and muffler may have 15k miles on it.They arced within 10 minutes. Dont think anything is wrong with the wires. Idles fine in park or neutral but but it gear and it ruff idles. Not arcing as bad as old wires but still arcing. Can't see it in day light but after dark you can see it., but barely.
 

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Discussion Starter #10
Yo swafford,

Spark Plug Wire Routing & Firing Order TSB 94-04-10 for 87-93 5.0 & 94-96 5.0 & all 5.8 - engine miss, spark knock, buck/jerk, surge and other driveability concerns;
● MIESK5 NOTE; The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark plug wires are routed next to each other at the separation bracket, an induction crossfire condition can occur.

See Routing @

Diagram for 5.0 in 87-90 Bronco, E 150, E 250, F 150, F 250; engine miss, spark knock in TSB 94-4-14
Source: by Ford via Chilton
Thanks I will check firing order. Dont have seperators but did route them and zip tied them so as they are not touching. It ran fine until the boots melted on the 3rd set of wires. That's why I bought the ceramic boots this time.
 

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Discussion Starter #11
Timing set correct new plugs. Wires separated, all boots connected but still arcing.
 
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