I hate to post without following my own advice and performing a visual of the computer internals, but alas it is raining outside if I were at home.



I am currently unsure and concerned about an engine miss fire.



3 weeks ago I changed spark plugs as a matter of routine maintenance and installed an accel supercoil. The truck drove fine for week as I needed/wanted it for some inclement weather.

Alas 2 weeks ago, guilt over forgetting to check/gap plugs 7 and 8 overcame me, so I gapped the plugs, and in the process 1 of the bluestreak 8.5 mm plug wires came apart on me.

Friday I was able to get back to my truck, installed new ford racing 9mm wires and an msd cap/rotor from Summit. I also spent a good part of the previous Saturday “nit picking” over my engine bay. Putting wire looms over frayed protector ends on pig tails and attempting to arrange connectors in their original spots though I am missing a couple brackets here and there. Honesty being the best foot to put forward, I did all this wigging and maneuvering of the wiring harness, without having disconnected the battery terminals. At one point I did hear a faint pop/pop noise I did not like as I lifted up the harness running behind the ac compressor, probably just the plastic and old tape creaking. Also I spent time just generally inspecting vacuum lines and tightened the valve covers, due to a new leak on each side of the engine.

To the point, when I first started my truck up, it sounded a little rough, but seemed to smooth out. After a drive I notice the gauge cluster temperature gauge wasn’t working but I did start to think my engine was shaking/vibrating rally hard between 30-50 mph, just generally what I would think symptomatic of a misfire. Sunday morning I corrected the gauge issue, just needed to pinch the wire connector on the sensor together a little.

I have double checked my cap arrangement and spark plug wire routing exactly as previously advised for all 5.8s and later model 5.0’s. My engine is a 92 5.8. After leaving the cap, 1-4 are separated and pretty much in order, 2 might cross under 3/4 prior to spacing. 6 crosses under 5/7/8 prior to spacing with the order above the valve cover being 5/7/8/6, 5 is almost direct, 6 comes over 7/8, 7/8 have the valve cover stud mount, then go each respective plug. Gaps are 0.054. My wire spacing holds the wires approx. 3/8” apart. If anything the Ford Racing wires are a little long for 7/8 and the ignition wire could be a lot shorter, I have it going down almost immediately and snaking above the fuel rail in a wire loom.

To dummy check the pcm quickly, the CEL self-checks like it should and my innova code spanner connected to it. KO/E0 tested SAT. KOER tested as it should, with one exception on the 1st of the 3 tests, I swear the first time I ran the KO/ER, it showed 6 for the cylinder count prior to flashing 10 for the user to blip the throttle. That test showed the expected code of thermactor air, and because I was staring at the scanner, codes for forgetting to turn the OD on/off and pressing the brake.
My 5.8 does have a significant amount of blow-by and the plugs are copper Motorcraft sourced from rockauto.

 

Spark crossfire in my experience does not cause a misfire, it causes pinging. The 5.8L firing order is not really susceptible to this anyway, it's the old 5.0 firing order that has the problem.

It sounds to me like you have your wires out of order more than anything. Check em again. The Ford wires should be numbered.

IMO you are wasting your money on the Accel coil and the MSD cap/rotor. Those are more for putting $$$ in the manufacturer's pocket than actually improving performance and they do not last as long as the OEM stuff.

 

As noted above recheck your spark plug wiring order as well as routing:

1994 and Up 5L All 5.8L Spark Plug Routing

 

I will not argue about it being wasted money as far as actually improving performance. Call it cosmetic though I hate the bright yellow Accel coil. I have the Ford wires installed by number, will check though for the 10th time. Anyone have an ultra trust worthy cap diagram to follow? I looked through the Chilton last night but do not recall if it had much of one. Definitely had nothing about wire routing causing misfires or pinging.

 

That is exactly the information I followed this time around. Does Dorman make the T-Stud wire separators at all? I managed to cram my wires in the separators on the side of the covers. I like to use a picture like this to write numbers on the top of the cap, before even starting a one for one cap replacement approach.

 

I went to change my plug wires, from Autozone Bestest's(on when purchased), I went as far as ohming the old wires, to compare to new(live wires) they are blue, anywho, I got a hi ohm reading on 2 of the new plug wires, and finally just removed the plug boot, and opened the plug fitting on wire and the suppressor(electrode) and could see the fiberglass core inside it so I cut and re-stripped and reinstalled them and miss went away, 2 days later the coil wire and same issue, sorry so long answer

 

Does the MSD cap have #1 marked on it? You just start there and go around the cap in direction of rotation with the firing order.

 

I snaked wire 3 to be on top and pushed the ignitions wire down under everything. Drove it around and am beginning to wonder if I am blaming a drive-train vibration on a misfire. Got back and greased my screaming U joints on the rear driveshaft. Took way too much grease. Then tried snugging up my exhaust manifolds with a 1/4 in ratchet while hot as well. Going to send it at 80 mph on the way to work tomorrow and see how it all feels. Preview attachment image0.jpeg
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I think its vibration in the driveshaft from the U-joints. If any odd vibrations at all were present this morning, it was only on acceleration. Once cruising at about at 76 mph, I really didn't discern anything, even with OD off a RPM higher on the hilly part of the highway.