Distributor cap issue

There are metalized and carbon dust and it could be the way of the construction
to trap'm to create lower resistance routing...

Or as said, the high voltage ignition wires may have the carbon filled fiber glass
strands compromised...so it finds a lower resistance path via the surface of the cap

On the engine oil mist...haven't heard of that in a long time...but
true.

Even poor lube to create that wobble and the old fix was to grind a
small groove on the shaft to allow some oil to seep down to the bearing

Dist's do wear out too and why one reason I use the best lubes can get
so help prolong the life span of this kind of stuff

distributor shaft bushings... any side movement on the shaft?

oil fumes and moisture can get by the bushings!

When was the last time you changed out the ignition wires?

If so, what kind?

What is interesting is that the way the cap is constructed the number 4 terminal actually passes right next to the number 2 terminal internally. I did read about moisture and it said to insulate the AC line that passes by the distributor. I still find it odd that it always number 2 and 4. If it was from moisture and carbon tracking I wouldn't think it would always be the same cylinder. It does have AC platinums in it. I may try a cap from the dealer next time. I put an Echlin from Napa on this time. It is the original coil on the truck. It is running fine now. I got my kids car fixed so he can drive it and now I am on to pulling the transmission out of the 03 to see what broke. It is a lot funner to work on cars when it is something you want to do instead of have to.

One other thing; if you have a moisture problem inside the cap, check the PCV system and change the oil. Water vapor can seep up the distributor shaft and condense on the cap as it is a bit cooler than the engine. Look at the inside of the oil fill cap for a milky substance which would be evidence of water in the oil.

your plugs have to be the ac delco platinum or it allows to much resistance in the cap and burns the wire inside

Do NOT touch anything inside the cap...or even blowing it clean with
your mouth...all it takes is that one tiny drop...

Do NOT hose off, pressure wash, etc around the dist, wires and plugs

Replace the wires with spiral wound SS *WIRE* that has an inductive
core that the wire is wound around. One of your leads could have gone
bad, going bad or been pulled to frey/break the carbon filled fiber
glass 'wire' conductor.

Use spark plug grease on both the cap and spark plugs

DO NOT do this while your hands are dirty. A finger print can become
the carbon track after one flash over

Check your coil...it maybe over voltage and/or have you gone to an
after market coil and/or system? When I had kit capacitor ignitions...some
times it would do this if everything was NOT perfect

Consider modifying your spark-plugs to have less resistance to the
jump over on the center to ground...or more correctly...takes less
voltage to jump employing the corona effect


My 8.1 is at 100,000. Time for plugs
CutBacksparkplug cutback


You can buy'm and only a few spark plug OEMs sells cut back spark plugs
NGK is my fav and they hand build these for racers & serious boy racers
$200 bucks EACH


Or you can make your own and is what I do for *ALL* my engines and
the whole HOW2 in the link above


cutbackplug cutback


PS...I'm not a fan of platinum plugs...they are just good enough
and are mainly for that 100,000 mile change interval...

I used to see this all the time when I was a mechanic years ago. Most of the time, it was caused by moisture intrusion which would cause a carbon track that will short one cylinder to another. What is interesting is that it is always the #4 to #2 path. My memory says that the firing order of your truck is 1,8,4,3,6,5,7,2. Since these wires are separated it's quite odd that it's always the same path.

Do a Google search on "Distributor Cap Carbon Track", and look at the images. See if you are getting the same type of path on your caps. If so, you need to keep all moisture out of the rotor cap area or you'll keep repeating the problem.

Have you bought a Delco from the dealer? Had similar issues with aftermarket wires on a 1999 4.3. Also fixed a buddys S truck 4.3 after he replaced plugs, wires, cap, rotor, intake gasket, map, tps, compression test etc. Told him to buy the cap rotor wires from the dealer. Ran perfect.

May not help you but just mentioning it. I have been to some GM factory training and was told to only replace the bad wires with the original equip one at a time as needed.