Dropped my car off at the dealership because of a cylinder miss fire :(

[Spork3245]

Got my car just under a year ago, just passed 5k miles on Wednesday. The FordPass App messaged me about a cylinder misfire on my way home from work Wednesday night (the service engine light was also flashing for a good 10 seconds when the miss fire occurred). Now, now, before people get all crazy and butthurt, this isn’t a thread complaining about “mah new car just broke! Ford smells!”, I love my 19 GT, and I never had any issues with my 2013 or 2016 GT, and just mostly regular nonsense on my 2001 GT Vert, these things happen and sometimes parts are defective.

So, why am I posting this? I’m just curious if anyone else had a similar issue on their 2018-2019 Mustang (or any other new car), what the issue was (I know it’s likely a defective spark plug, but, it could be something deeper that caused the spark plug to go bad), and how lengthy the fix took. The dealership comped me a loaner... a 2018 base-level Escape (kill me) and I’m just wondering how long you guys think till I have my sweet GT back (dealership is looking at it late today or early tomorrow, my appointment was originally scheduled tomorrow but they asked me to drop it off this morning to ensure I got a loaner).
Thank goodness for warranties!

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[RozzGT]

Which cylinder? Mine last one did this on cylinder 8 and it ended up being the IMRC flap broke on the intake manifold. Somewhat common issue but always throws cylinder 8 and sometimes multiple misfire along with it.

 

[Deleted member 35644]

For me, both times I had a misfire (Mazdaspeed 6) it was a coilpack.

 

[DuRsT]

Had a misfire on my '13 and it was a coil pack with about 5k miles on it as well.

 

[Spork3245]

UPDATE:
So, their scanner is stating it's a misfire on cylinder-4. They pulled the spark plug, fuel injector, AND coil pack. Everything looked normal. It seems to also be driving normally when they took it out (the car drove normally after the engine light stopped flashing and prior to the engine light flashing on Wednesday night, as well as this morning on the drive to the dealership). They put in a call to Ford's tech department to see if they've encountered anything like this before, in the meantime (as they don't expect a call back until late in the week) they said I could pick my car up as "it doesn't seem like any damage is occurring" so the techs aren’t worried about a few more miles being put on it until they hear back from Ford.

 

[Spork3245]

Which cylinder? Mine last one did this on cylinder 8 and it ended up being the IMRC flap broke on the intake manifold. Somewhat common issue but always throws cylinder 8 and sometimes multiple misfire along with it.

Cylinder 4

 

[Spork3245]

BTW (sorry, not trying to spam my own thread!) this happened back in late February or early March (can't remember exactly), but the FordPass app notified me about it like 3-5 weeks after it happened, and the car was driving normally that whole time as far as I could tell. If I'm remembering correctly, the day it was stating was a sub-freezing day temp wise (like 12F) and the car was only running for 10-15 minutes (that's the distance my business is from me) and I probably had to do a semi-hard acceleration to merge onto the highway out of this one jug-handle, and when it happened on Wednesday, the car was only running for maybe 5-ish minutes (though I don't think I accelerated hard, it may have been in Sport-mode...?) and it did occur after going from a stop at a red light. SO, could this be simply from the engine not being totally warmed up enough or whatever?

 

[FatBurritoEater]

What kind of fuel do you put in it out of curiosity? I had a CEL flash during hard acceleration extremely early on in my ownership with 87 octane, and I've never had an issue since (use 93 consistently).

 

[Spork3245]

What kind of fuel do you put in it out of curiosity? I had a CEL flash during hard acceleration extremely early on in my ownership with 87 octane, and I've never had an issue since (use 93 consistently).

I only use 93.

 

[ElCid08]

Which trans do you have? 10R80 or MT82? Out of curiosity

 

[Deleted member 35775]

Got my car just under a year ago, just passed 5k miles on Wednesday. The FordPass App messaged me about a cylinder misfire on my way home from work Wednesday night (the service engine light was also flashing for a good 10 seconds when the miss fire occurred)...... I’m just curious if anyone else had a similar issue on their 2018-2019 Mustang (or any other new car), what the issue was (I know it’s likely a defective spark plug, but, it could be something deeper that caused the spark plug to go bad), and how lengthy the fix took. ......
Thank goodness for warranties!

Which cylinder? Mine last one did this on cylinder 8 and it ended up being the IMRC flap broke on the intake manifold. Somewhat common issue but always throws cylinder 8 and sometimes multiple misfire along with it.

yep, i had a similar misfire issue as well. i ignored the first 2 messages from the FordPass App but the third triggered a problem code and Ford replaced the manifold because the IMRC wasn't functioning properly. once Ford approved replacement, it took the dealership 1 day to fix it. dealership also replaced all the spark plugs. no issues since it was fixed and i am still able to hit 140 MPH with no issues. FYI - the 140 MPH run was on a private 2 mile road with a 1.6 mile straight away.

 

[Spork3245]

yep, i had a similar misfire issue as well. i ignored the first 2 messages from the FordPass App but the third triggered a problem code and Ford replaced the manifold because the IMRC wasn't functioning properly. once Ford approved replacement, it took the dealership 1 day to fix it. dealership also replaced all the spark plugs. no issues since it was fixed and i am still able to hit 140 MPH with no issues. FYI - the 140 MPH run was on a private 2 mile road with a 1.6 mile straight away.

Which cylinder was it for you?

 

[Deleted member 35775]

Which cylinder was it for you?

i believe it was 3 and 8; codes were P0300, P0303 and P0308.

 

[Spork3245]

i believe it was 3 and 8; codes were P0300, P0303 and P0308.

Mine seems to only be cylinder 4, but, I’m going to mention the intake manifold thing regardless tomorrow. They’re likely going to still wait to hear back from Ford, but at least it’s something.

 

[Deleted member 35775]

Mine seems to only be cylinder 4, but, I’m going to mention the intake manifold thing regardless tomorrow. They’re likely going to still wait to hear back from Ford, but at least it’s something.

great, by the way, IMRC = Intake Manifold Runner Control. hope your car is fixed soon!

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