7.3 2021 with 850 miles and coding for multiple misfires... taking to dealer on Thursday as last drive was nothing but a misfire code nightmare...

MECCA60

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800 miles and very mildly driven to date... Misfire issue, spark boots all look good, but obviously something is definitely wrong as literally 15 minutes into a highway commute check engine amd misfire codes started to accumulate... thinking maybe bad gas or is this the signs of the spark plug wire issue already on a tsb? Set a Dealer appt for Thursday as it’s obviously warranty and don’t want to play around so new...
 
I had a problem a couple of months ago after buying some gas from a sketchy rural station. It was near an ethanol plant so they had about six different varieties of ethanol. I'm pretty sure I bought the non-ethanol version but is possible that the tank had some water in it. After burning through the tank to near empty and getting a new full tank the problem went away. I wonder if the sensor on the 7.3 is especially sensitive to gas with some water in it. Or old gas.
 
800 miles and very mildly driven to date... Misfire issue, spark boots all look good, but obviously something is definitely wrong as literally 15 minutes into a highway commute check engine amd misfire codes started to accumulate... thinking maybe bad gas or is this the signs of the spark plug wire issue already on a tsb? Set a Dealer appt for Thursday as it’s obviously warranty and don’t want to play around so new...
 
<<<Update>>>
Truck at dealer for 10 days and after numerous dread ends chased by tech, they basically claimed the truck had a “loose coil/plug” wire on Cylinder 4, and that now Cylinder #1 was actually showing a “misfire” only on their console analyzer....
Though not throwing a code on truck, so they give it back to me and stated “watch” and return it if CEL returns...

Factory FORD tech suggested they start to disassemble engine if code returns, that’s not news I want but alas NO codes and I burned through an entire tank of fuel today just to really give it a run...

I’ve got replacement wires redied to do my own “test” IF codes return...

I’m skeptical to say the least with what Ford is doing here, they didn’t even touch the wires other than “reseating” number 4... WTF you would think that’s one of the first places they go after verifying coils are firing... especially since they had the TSB out on this in 11/2020 for the RV chassis 7.3....
 
<<<Update>>>
Truck at dealer for 10 days and after numerous dread ends chased by tech, they basically claimed the truck had a “loose coil/plug” wire on Cylinder 4, and that now Cylinder #1 was actually showing a “misfire” only on their console analyzer....
Though not throwing a code on truck, so they give it back to me and stated “watch” and return it if CEL returns...

Factory FORD tech suggested they start to disassemble engine if code returns, that’s not news I want but alas NO codes and I burned through an entire tank of fuel today just to really give it a run...

I’ve got replacement wires redied to do my own “test” IF codes return...

I’m skeptical to say the least with what Ford is doing here, they didn’t even touch the wires other than “reseating” number 4... WTF you would think that’s one of the first places they go after verifying coils are firing... especially since they had the TSB out on this in 11/2020 for the RV chassis 7.3....
Update I placed new wires on for test and engine immediately started to “smooth out” at idle… These factory wires ARE the problem. Not happy with Ford as obviously they are playing games with this issue, and either not getting new parts quick enough or playing their old “warranty games” yet again…
 
Cylinder #2. Wire decided to quit in De Witt IA last Friday evening. Auto parts stores couldn’t get one till Monday. Not a bad stay and slapped it in Monday morning. Runs like new. Bought a spare wire!
 
Cylinder #2. Wire decided to quit in De Witt IA last Friday evening. Auto parts stores couldn’t get one till Monday. Not a bad stay and slapped it in Monday morning. Runs like new. Bought a spare wire!

Wonder what is really going on with these plug wires. I'm not sure I've ever seen a failed plug wire on any gas vehicle in my entire life but Ive seen this issue come up with this 7.3 from several people. Based on seeing how it melted some aftermarket wires in other threads it makes me think there is some major heat on them around the exhaust manifold...hopefully they get it straightened out.
 
Wonder what is really going on with these plug wires. I'm not sure I've ever seen a failed plug wire on any gas vehicle in my entire life but Ive seen this issue come up with this 7.3 from several people. Based on seeing how it melted some aftermarket wires in other threads it makes me think there is some major heat on them around the exhaust manifold...hopefully they get it straightened out.
Funny thing here is I had never seen a plug wire issue like this until about 2 years ago. My brand new pressure washer has a metal heat shield around the plug boot. After running or a fair mount of time, the engine popped and died, and would not restart. After checking the gas, the switch, the oil, and everything else, I pulled the plug wire off and it came apart at the boot with very visible burn marks inside the boot. It appeared that it was arcing through the wire and boot to the metal heat shield. Kohler coved it under warranty. This past weekend, it appears it has done it again.....
My thoughts are that it may be about the same issue with the Ford plug wire sets and the metal heat shield...but that just my 2 cents worth.
 
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800 miles and very mildly driven to date... Misfire issue, spark boots all look good, but obviously something is definitely wrong as literally 15 minutes into a highway commute check engine amd misfire codes started to accumulate... thinking maybe bad gas or is this the signs of the spark plug wire issue already on a tsb? Set a Dealer appt for Thursday as it’s obviously warranty and don’t want to play around so new...
I had a 2020 tremor 7.3 that put out a total of 49 misfire codes at 281 miles. The dealer then had it for 30 days. The took the heads off. They said there was some bad engine blocks early in production & the oil & cooling galleys were not opened up during the castings. The Ford dealer recommended I filed a lemon law claim with FOMOCO & now I have a 2021 Tremor 7.3 with 10K miles & a trouble free history. They also gave a check for $2500 towards another truck If was willing to buy another Ford product. Ford was very cooperative & handled my claim very quickly. Paid for the rental truck for the month & a half I had it too. It was actually an unbelievably easy process.
 
Funny thing here is I had never seen a pug wire issue like this until about 2 years ago. My brand new pressure washer has a metal heat shield around the plug boot. After running or a fair mount of time, the engine popped and died, and would not restart. After checking the gas, the switch, the oil, and everything else, I pulled the plug wire off and it came apart at the boot with very visible burn marks inside the boot. It appeared that it was arcing through the wire and boot to the metal heat shield. Kohler coved it under warranty. This past weekend, it appears it has done it again.....
My thoughts are that it may be about the same issue with the Ford plug wire sets and the metal heat shield...but that just my 2 cents worth.
This is just a guess, but small engines are running leaner to meet CARB emissions regs, therefore hotter.

Also, I bet there are only a half dozen suppliers for spark boots and wires. Maybe they went cheap and made the material less resistant to heat?

I put over 300,000 miles on GM 5.3L with the same setup as the 7.3. Never an issue over 20 years. Seems that Ford forgot how to test or spec these given all their time with the modular platform using coil on plug.

Hope mine works. I'll carry a few spares.
 
Cylinder #2. Wire decided to quit in De Witt IA last Friday evening. Auto parts stores couldn’t get one till Monday. Not a bad stay and slapped it in Monday morning. Runs like new. Bought a spare wire!
@mothra get a couple more to throw under the seat and an OBD2 mx+. You may want to look at these also (LC3Z-12286-C), slightly different wire on the MH chassis.
 
This is just a guess, but small engines are running leaner to meet CARB emissions regs, therefore hotter.

Also, I bet there are only a half dozen suppliers for spark boots and wires. Maybe they went cheap and made the material less resistant to heat?

I put over 300,000 miles on GM 5.3L with the same setup as the 7.3. Never an issue over 20 years. Seems that Ford forgot how to test or spec these given all their time with the modular platform using coil on plug.

Hope mine works. I'll carry a few spares.
Talking it through with my rocket scientist electrical engineer father-in-law and he believes it’s a high rpm and bad crimp design. All of my failures occurred towing on grade and all are at the connection from the wire to the boot. After he inspected the failed Massive wires, he believes at high rpm we’re generating too much heat at that connection and it can not dissipate fast enough which causes the failure. Ford recommended coil, wire and plug replacement of my 7.3L but I could not wait until late August for the parts.
 
Talking it through with my rocket scientist electrical engineer father-in-law and he believes it’s a high rpm and bad crimp design. All of my failures occurred towing on grade and all are at the connection from the wire to the boot. After he inspected the failed Massive wires, he believes at high rpm we’re generating too much heat at that connection and it can not dissipate fast enough which causes the failure. Ford recommended coil, wire and plug replacement of my 7.3L but I could not wait until late August for the parts.
He has a good point. this got me thinking...

Given what you said, I wonder if Ford specified a spark plug that is too hot for the high load conditions? FYI, a "cooler" plug moves more heat from the plug to the head, a "hotter" plug retains more heat.

This gives more info... https://www.denso.com/global/en/pro...e-parts-and-accessories/plug/basic/heatrange/

So, a "hot" plug won't dissipate heat as well, which, over a long enough period of time, this heat would travel up the electrode and into the plug wire.

It would be interesting to see if anyone could run a cooler Iridium or Ruthenium plug. would take a lot of time and testing.

Not cheap at $15-$20 each, but worth considering.
 
So I just started a long road trip with the fifth wheel. Every time I hit a steep upgrade and transmission shifts down and rpms hit 4000+, it misfires. A scan shows #7 cylinder. Truck runs fine other than this. It's been through 5 tanks of gas across 3 states so I don't think it is that. I tried premium for two tanks as well. I have replaced that spark plug wire this morning and I guess we'll see. By the way, I was running the Massive wires and replaced with stock. The Massive wire was slightly melted so I cannot recommend that. The exhaust manifold is really close to the wire.
 
So I just started a long road trip with the fifth wheel. Every time I hit a steep upgrade and transmission shifts down and rpms hit 4000+, it misfires. A scan shows #7 cylinder. Truck runs fine other than this. It's been through 5 tanks of gas across 3 states so I don't think it is that. I tried premium for two tanks as well. I have replaced that spark plug wire this morning and I guess we'll see. By the way, I was running the Massive wires and replaced with stock. The Massive wire was slightly melted so I cannot recommend that. The exhaust manifold is really close to the wire.
My misfires also came on grade above 4k rpm. I think it may be more than the heat from the manifold. My massive wires looked like they were possibly heat at the crimp connector. I really think there’s something happening there which is generating heat and melting from the inside out. Also keep a eye on your battery for fluid on the top. I also boiled mine over a couple of times.
 
Wow, glad I went for the 6.7L. I considered the 7.3L but I had the V8 Triton, 5.3L I think, I forget, in my '03 F150. I had to keep replacement coil packs under the seat. Since then, it has been all diesel for me.
 
Update: I replaced the one massive wire that melted with factory wire and cleared the codes. Ran another 650 miles today hard towing. Truck ran beautifully.
I am running a little over 21k gcvw. The transmission allows you to be in the right gear for the speed you want to go. No problem with power regardless of the grades. Never got hot and this is in 95-100* heat, high elevations (5-7200 ft) average fuel economy is 7.8 mpg with hard driving.
 
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