As long as your wires are high RMI, EMI shielded, that routing is not necessary at all. Just get some top quality cables. Not Autolite, or Napa, Autozone or most other fast food type auto store brands, but, good wires like Moroso or Taylors.

I would stay away from MSD wires. I have had a set of their super conductors and they were problematic to say the least. One went completely dead- no continuity and, three others show breaks in continuity under flex testing. I don't like the way they crimp those and I don't like the ends they use. They employ a pinch design vs. a fold under design. Those termination ends tend to also bend apart thus making a sloppy connection at the plug.

In my opinion and experience, both Taylor 50s and Moroso Ultra 40s are higher quality wires than MSD. So, as long as your running good wires and, the coil wire is shielded really well, you won't have any issues with crossfires and misfires.

It's only the cheaper wires that have an issue with this due to a lower dielectric properties of the insulation. This allows the high voltage to jump to a neighboring wire or arcing to the block. Just be sure to route them nice and neat and you won't have an issue.

 

make sure u got the right fire order you might have put the wrong wire on the wrong plug if u just changed all that stuff thats what i would check first

 

Ok, if the tip is white, here's what I think your problem may be. White tip is indicative of running hot. It is quite possible that your CAT is restricted and, because of this, the heat is backing up into the headers and into your cylinders thus inducing a misfire due to excessive heat.

Are all the plugs white or just one or two of the rear ones white???????
This will tell me where to look if all are white or just seven and eight are white. Two different modes of failure here; lean condition and clogged or restricted CAT.

With that many miles, get a new CAT if you haven't done so already. That could be the issue. Now, had you not mentioned the bit regarding the white tip on the plug, it could have been many things from a lean condition, to a CAT, to altitude changes and running a hot coil, to bad plugs, to crossfire due to cheap ignition wires to a dead or weak cylinder / no / lack of compression.

Basically, what your looking at is either no spark, no compression, or no fuel or timing. Now, when you use a tree to show all that's under those, it blossoms out and gets involved.

So spark leads us from the battery to the ASD relay to the coil to the coil wire to the cap, to the button inside the cap, to the rotor and to the contact at each cylinder to each plug. Now, to test all those, you can either do what you did and simply swap out the coil but, that's not really going to show you anything other than a coil for coil test.

What we needed to do was to measure the coil first at the primary and secondary and compare it to OEM specs. IF all is good, we move on to the next step: power to the coil.

So, now we check all the wiring involved. You would have taken the connector off the coil and ohm'd out the power wire (green/ orange wire to the PDC (Power Distribution Center) and found it to be ~1 ohm or high resistance. High resistance means you have a bad feed. 1 ohm and your good to go.

Next: check the ground from the coil to the PCM at the connector. It will be on the black connector. There's three connectors at the PCM and, starting from the left it is grey, white and black. Remove all three and find the corresponding pin for that ground at the coil on the bottom row. I can't recall the exact pin but, you'll find it when doing a continuity test.

We would also test your ASD relay and your fuel pump relay to ensure those are not of high resistance across the pins. We would simply measure the ohms across the pins unpowered and while powered. If all checks out, we now know that all in this coil circuit is capable of delivering the proper voltage to the coil.

Once that checked out @ ~1 ohm, you would now look at whether or not the PCM is switching the coil on and off or, if it's a solid voltage- your PCM is gone and needs to be replaced. To do this, all you have to do is NOT use a DMM or DVM ( due to damage being done to the PCM) but, you would take a cheap test light for 5 bucks or, you could get the better, LED lights that go on / off where you can see this vs. a light bulb that uses a filament.

Backprobe the positive (+) connector of the coil and attach the ground (-) to frame ground. The headlight ground is within safe reach. You should see a steady light with the truck running.

Next up, let's check the ground side. Backprobe the connector at the ground (-) and connect the other side to ground. Run the truck. You should now see a flashing light. This means your PCM is good.

So, there's how you rule out your coil. Now, there's also, another test but, you are sure to kill yourself if you have no experience or posses the proper tools. This measures the output in KV. This checks your coils output. Again, I am not going to instruct you how to do this test because I do not want to see you get fried. Take it to a shop where they can measure it for you.

I have seen many coils and transformer types of things measure fine on the bench but not put out the correct voltage or, have it be intermittent or, under load conditions and coupled with high thermal loading, they crap out.

Next we would be looking at your cap for it being eaten. Eaten by what? Your distributor or a super hot coil. If you have excessive end play (up and down) it will rise up and grind down the center contact. I have melted my contacts running too hot of a coil. If your running stock coils, It's a non issue.

If you have excessive run out on your distributor shaft, (this is a side-to-side movement of the dizzy due to worn out bearings and bushings) it will oval out and eat the contacts in the cap. If the gear is excessively worn, the timing drifts in and out and, at higher rpms, cause misfires.

Next up, after checking the cap, we would go through and check each plug wire for resistance. Lower the better. Max resistance is 25k ohms per wire.

If all your wires check out, we would move on to checking the voltage at each spark plug. Again, due to death by means of electrocution, you can not do this without a calibrated tester safely. The crude methods of shorting it out to the block is a good way to kill yourself if your in contact with ground and it arcs over to you to ground, and secondly, it is not going to tell you what the voltage is at each plug. This is essential to keying in to what may be causing your misfire. While I have done this many times myself in the past, I highly discourage the arc to ground method.

Now, beyond that, we could also do a power balance test as well and while under load. But, that's way beyond the scope of simple so, let's move on.

Then, we would run a compression test to see if you have a dead or weak cylinder. Loss of compression going uphill would cause a misfire for sure.

IF that checked out to somewhere around >100 on each cyl, we could say, it's ok. Spec is 150 ± 20%.

Next up, we would then check your A/F mixture and see if your running a lean condition. Running lean is one thing but, very lean results in not enough fuel to burn thus causing no burn thus triggering a fault code or misfire.

Now, what causes a lean condition? Low fuel pressure for starters and, or, too much air flow vs. fuel. This is when people throw huge 57MM TBs on a stock engine and wonder why their truck runs like junk. It's now getting too much air and not enough fuel. Even with the PCM and O2 sensors adjusting the trims on the fuel, it's simply not enough to overcome the volume of air coming in.

But, that's on modded applications, in a stock setup, we have to check your fuel pressure and make sure that it is within OEM specs. Depending on which fuel injectors you have also makes a difference but, if it's OEM spec, it's most likely the stock 22s.

Now, it's not just the fuel pump that can cause a lean condition but, also, clogged or restricted fuel injectors. This is often, the most overlooked part of the engine. Those FIs do not last forever and, they do clog up with fuel deposits as well as other debris.

We would then remove all the injectors and test them for flow rate and see if they need cleaning or not. Now, the cleaning I am talking about is not the kind of cleaning where you throw something in the gas tank and run it through the injectors but, this is a pro-service where, we pull them off and run them on a machine and measure them both electrically and mechanically.

With that many miles, you may find that they are not in good shape if they are the OEM stock ones. I recommend having them tested. if you would like, I can test them for you. PM me for details if need be.

In addition to spent FIs, you may also have an out of whack O2 sensor that's telling your PCM that your running rich. In turn, the PCM keeps trimming more and more off until you get misfires.

Now, as it was mentioned earlier, you may just simply have a crossfire condition going on with those ignition wires. Who makes the wires your running?

The best thing is to start off with the simple stuff first. Rule all the simple and easy stuff first. Then proceed to the more involved areas.

One thing to do would be to bring it into a shop where they have data loggers. We would take it out, record the data and look at it later to see what the issues were under load and while driving.

But, it just me something very very simple to remedy yourself and without a huge out of pocket expense.

Hope that gives you an understanding of what's involved.