MIL on/P0302 Misfire - 2025 Maverick 2.0 EB

[john21161]

A week ago my 2025 began misfiring on acceleration. The MIL (check engine light) was flashing, indicating a continuous misfire. I backed off the throttle and the misfire stopped. The MIL remained on solid. Pulling over, I cycled the ignition off/on and the vehicle started and idled. The MIL was still illuminated. Since we were near home, I could drive back gently, under light throttle and everything seemed normal.

Back home, I was able to read a P0302 engine misfire/cylinder two/continuous code. I tried clearing the code - NOT RECOMMENDED, by the way, as it will complicate your warranty work at the dealer - and drove the vehicle down my driveway. As soon as I encountered a steep hill, the misfiring returned. Again, at idle and light throttle, the engine performed normally...as soon as any load was applied to the engine, it began misfiring. I limped back home and called the dealer to arrange to have the vehicle brought in.

Since the misfire was significant and I didn't want to cause any more extensive damage to the engine, I decided I should have my vehicle towed the 30 miles to the dealer. It was a week before I could get an appointment. Wednesday, the wrecker picked up my Maverick.

I got a call from the service advisor yesterday to say they had received the vehicle and would begin diagnosis. We reviewed my information and I was told to expect a call when they knew something. About 3:30 the service advisor called and told me that they "had found two spark plugs (Cylinders 2 and 4) were melted." I have no idea what would cause a 13,000 mile engine to "melt" two plugs? Massive over boost? The SA asked me if I had tuned the vehicle...I have not. It's bone stock, except for an aftermarket exhaust system.

This is all the info I have at the moment. I will pick up my truck later this morning and we will see what is what.

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[Clarkdonbran]

 

[john21161]

I know, right! How'd you break it this time?!

 

[john21161]

Follow up: Drove the Maverick back from the dealer. Everything seems to be working normally.

Repair order contains standard (I assume) diagnostic procedure: verified CEL, verified misfire no.2 cylinder, performed "injector flow test", injectors passed, removed no.2 spark plug and found, "strap (ground electrode?) on plug was melted. Tech test drove the vehicle and still detected engine misfire with something called an FDRS (Ford Diagnostic Repair Scope?) and found no.4 cylinder was also misfiring. He then removed the other 3 plugs, replacing no.4 and verifying that 1 and 3 were ok.

That's what I have got right now. Two warranty spark plugs and have a nice day.

Speculation: Being old...the only stuff I remember causing spark plug ground electrodes to "melt" would be some sort of serious detonation or pre-ignition condition. I'm unsure if too much turbo boost or something like that might also cause those kind of pressures? Surely, the FORD engine control programming must have some sort of fault detection parameters for this, stuck waste gate etc? This is definitely out of my area of competence.

I have been running regular 87 octane gas in the Maverick this winter, as opposed to the 93 premium I was using over the summer. But, I can't be the only 2025+ Ecoboost owner to run regular gas, am I? In any event, on the way home I stopped at Sunoco and filled up with 93, just in case. I will keep you all posted on any further developments.

 

[Chops]

A week ago my 2025 began misfiring on acceleration. The MIL (check engine light) was flashing, indicating a continuous misfire. I backed off the throttle and the misfire stopped. The MIL remained on solid. Pulling over, I cycled the ignition off/on and the vehicle started and idled. The MIL was still illuminated. Since we were near home, I could drive back gently, under light throttle and everything seemed ..

Is your build date between 10/24 and 5/25?

There is a TSB for this large swath of vehicles FYI - probably unrelated to your situation but figured I mention it:



“SSM 54138 2024-2025 Various Vehicles - 1.5/2.0/2.3/3.5L EcoBoost - Extended
Crank, Fuel Smell In Engine Oil And/Or High Engine Oil Level - Built On 01-Oct-
2024 And Through 31-May-2025

Some 2024-2025 F-150, Expedition/Navigator, Escape/Corsair, Bronco, Explorer, Mustang, Maverick vehicles
equipped with a 1.5/2.0/2.3/3.5L EcoBoost engine and built on 01-Oct-2024 and through 31-May-2025 may
exhibit an extended crank condition, strong fuel smell in the engine oil, high engine oil level and may have
various drivability diagnostic trouble codes (DTCs) stored in the powertrain control module (PCM) with an
illuminated malfunction indicator lamp (MIL). This may be due to an internal fuel leak of the fuel injection pump
causing fuel to enter the crankcase and reduce fuel pressure in the high pressure fuel rail. Diagnose this
condition using Pinpoint Test HP located in the Workshop Manual, Section 303-04A. If no DTCs are stored in
the PCM, proceed from Step HP1 to Step HP5 and continue testing. For claiming, if fuel injection pump
replacement is required, use causal part number 9D376 and labor operation code 9543A. If the root cause is
identified as anything other than the fuel injection pump, claim the repair outside of this article. Note:
Components damaged as a result of this failure mode should be repaired and claimed outside of this article.”

 

[Chops]

Follow up: Drove the Maverick back from the dealer. Everything seems to be working normally.

In any event, on the way home I stopped at Sunoco and filled up with 93, just in case. I will keep you all posted on any further developments.

I don’t mean to be a dick - but Sunoco is not Top Tier gas. Ford recommends Top Tier.

As a fellow owner of a 25 EB, I appreciate your explanations of this ongoing situation.

 

[Cherokee]

Back in the day an exhaust leak, header leak or open pipe condition or a cc removal could and sometimes did lower exhaust back pressure to the point of cooling the exhaust valves to temps out of spec.
This was known to destroy a spark plug or burn a compression ring.
This type of a condition was not always something you would hear.

You said you modified the exhaust, did you remove a converter possibly sidelining the stock fuel map and causing a lean burn condition ?

The fuel type, or quality or octane IE top tier or cheap shit or regular or 93 octane would not play a roll in cooking a plug.

It could be as simple as who ever did your pipe welding did a piss poor job.

Back in the day taking an EFI Harley to Stage one, would destroy a plug and burn valves if you did not correct the fuel air mixture.
The stock fuel air system has a limited range and can only do so much to comp for air flow changes.
Sounds like a too lean mixture.

If it cooked a couple of plugs I’d suspect your destroying compression rings, valves, Valve seats and possibly pistons.
If so this will show up in short order.

 

[Chops]

Dirty fuel injectors can trigger a P0302 & melted plugs?

If I were using non Top Tier gas - I’d pour in some Motorcraft Fuel Injector Cleaner every 3000mi & keep receipts.

Techron is half the price and just as (more) effective - but using Motorcraft might make a warranty issue easier to deal with.

 

[Cancunbadlands]

Didn't Ford say anything about the aftermarket exhaust system??????

 

[Chops]

Didn't Ford say anything about the aftermarket exhaust system??????

My local Ford Dealer recommended and ordered my Borla X-Type catback for me. They were not honoring a 20% Ford discount on the Ford Performance Exhaust & suggested the less expensive Borla. Anyway, I picked it up at the dealer & installed myself.

Ford does not care what you install behind the CATS…they don’t even offer any type of warranty coverage on their OEM pipes behind the CATS.

 

[zorki1c]

Sorry. No way you should have to run gas above 87 octane. You get a truck with engine that should give you better mileage and save money then pay more for high octane “top tier” gas.
I’m guessing a modified exhaust is more likely a problem. I don’t go on othe vehicle forums but seems like a lot of Mav owners seem to think they must immediately do everything they can to improve performance. Why? If your little truck isn’t powerful enough for you taste get a truck the comes stock with better performance.

 

[john21161]

Thanks for the replies everyone.

I don’t mean to be a dick - but Sunoco is not Top Tier gas. Ford recommends Top Tier.

As a fellow owner of a 25 EB, I appreciate your explanations of this ongoing situation.

I appreciate the heads up on the TSB. My build date is late 3/25...so, right in the middle of that. I did check the oil for fuel smell before I had the repair done. Negative, it just smelt like oil.

You're not being a dick, at least I don't think so. I would have had NO idea that SUNOCO wasn't top-tier fuel...so, I looked it up on the Top Tier website and that SUNOCO station is on their list. So, I'm good.

 

[john21161]

Back in the day an exhaust leak, header leak or open pipe condition or a cc removal could and sometimes did lower exhaust back pressure to the point of cooling the exhaust valves to temps out of spec.
This was known to destroy a spark plug or burn a compression ring.
This type of a condition was not always something you would hear.

You said you modified the exhaust, did you remove a converter possibly sidelining the stock fuel map and causing a lean burn condition ?

The fuel type, or quality or octane IE top tier or cheap shit or regular or 93 octane would not play a roll in cooking a plug.

It could be as simple as who ever did your pipe welding did a piss poor job.

Back in the day taking an EFI Harley to Stage one, would destroy a plug and burn valves if you did not correct the fuel air mixture.
The stock fuel air system has a limited range and can only do so much to comp for air flow changes.
Sounds like a too lean mixture.

If it cooked a couple of plugs I’d suspect your destroying compression rings, valves, Valve seats and possibly pistons.
If so this will show up in short order.

Yes, I agree with you that an exhaust leak could cause a lean condition, if the fuel system couldn't compensate enough. However, the exhaust system I have is a post cat type system. It's been on the vehicle since almost new (700mi) and I've not had any issues up till now.

Also, I would have thought that any fueling condition, rich or lean, that would be severe enough to melt plugs, etc would have triggered a bunch of fault codes? In Toyota EFI systems, anytime Long Fuel Trim went + or - greater than 20%, it would light up the MIL/CEL. Ford might be different...but, I thought the basic parameters needed to be met by all manufacturers?

As for the valves, rings, pistons, etc. Well, yeah I would be concerned about this also...I guess we'll see?

 

[john21161]

Didn't Ford say anything about the aftermarket exhaust system??????

No, not a word. He did ask if I "had tuned it." Nothing about the exhaust system.

 

[john21161]

Sorry. No way you should have to run gas above 87 octane. You get a truck with engine that should give you better mileage and save money then pay more for high octane “top tier” gas.
I’m guessing a modified exhaust is more likely a problem. I don’t go on othe vehicle forums but seems like a lot of Mav owners seem to think they must immediately do everything they can to improve performance. Why? If your little truck isn’t powerful enough for you taste get a truck the comes stock with better performance.

Actually, performance was fine for me. It was just too quiet. I just wanted a little more motor sound, so I got the quietest system I could find for my model/year. It's ok, not super loud, but drone is still noticable under load.

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