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

[Spork3245]

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

Missed your question yesterday! I have the 10-speed auto.

Picked up my car this morning, mentioned the IMRC, he said that they probably did check that but that all tests were coming back normal, but he said that definitely could be the cause, however they have to wait to hear back from Ford before doing anything since there were no additional error codes on the tests they did.

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[IronG]

Missed your question yesterday! I have the 10-speed auto.

Picked up my car this morning, mentioned the IMRC, he said that they probably did check that but that all tests were coming back normal, but he said that definitely could be the cause, however they have to wait to hear back from Ford before doing anything since there were no additional error codes on the tests they did.

So when they scanned your car they did not see any codes or they are dismissing it as normal because it only happened once?

 

[ElCid08]

Interesting. I asked because I just went through the buyback process with Ford for my 2018 GT that started off as a misfire on one cylinder (number 4 I think). 10spd auto car as well. They tried a few things and gave it back to me twice. Kept happening and turned into misfires on all 8 cylinders. Dealership still had no clue 25 days in. They called in a Ford field engineer (who never showed up once I hit the 30 day mark and requested a buy back). Long story short, it sat for 60+ days at the dealer while I navigated through the buyback process. Car had 4100 miles on it when it first went in. I really hope yours isn’t as serious and they get it figured out!

 

[Spork3245]

So when they scanned your car they did not see any codes or they are dismissing it as normal because it only happened once?

No, there was a code that there was a misfire on cylinder 4, what came back normal are all the tests on the parts that they tested (definitely tested: spark plug, coil pack, and fuel injector. maybe tested: IMRC). They have to wait until they hear back from Ford because everything is testing normally and it's warranty work, so unless Ford goes "it's probably part X, replace that" they can't. They aren't dismissing anything (yet).

 

[gj]

Far out they must be shit mechanics if they can't trace a miss fire.
Seems unbelievable they would buy back a car over something like that

 

[Spork3245]

Interesting. I asked because I just went through the buyback process with Ford for my 2018 GT that started off as a misfire on one cylinder (number 4 I think). 10spd auto car as well. They tried a few things and gave it back to me twice. Kept happening and turned into misfires on all 8 cylinders. Dealership still had no clue 25 days in. They called in a Ford field engineer (who never showed up once I hit the 30 day mark and requested a buy back). Long story short, it sat for 60+ days at the dealer while I navigated through the buyback process. Car had 4100 miles on it when it first went in. I really hope yours isn’t as serious and they get it figured out!

That's insane, you think they'd just replace all the spark plugs, coil packs and possibly the IMRC before giving up and doing a buyback. JFC.

 

[ElCid08]

I think they tried it all. Weirdly, the nav/sync 3 screen went blank right when the first misfire popped up. Screen was back on the next morning, but the misfires, and loss in power was still there. It was pretty unbelievable to me as well. Purchased brand new in late late December of 18’, and bought back in June of 19’. I kid you not, I was told Ford was coming to pick the Oxford White car(the 18 GT lemon) up from the dealership, take it to some facility and rip the entire thing apart, figure out the issue, and crush it when they were done. I still have complete faith in my dealership and the service department. Just a 1 in a million fluke I hope. I put 3400 miles on the loaner Edge that I had the entire time mine was at the dealership.

 

[IronG]

I think they tried it all. Weirdly, the nav/sync 3 screen went blank right when the first misfire popped up. Screen was back on the next morning, but the misfires, and loss in power was still there. It was pretty unbelievable to me as well. Purchased brand new in late late December of 18’, and bought back in June of 19’. I kid you not, I was told Ford was coming to pick the Oxford White car(the 18 GT lemon) up from the dealership, take it to some facility and rip the entire thing apart, figure out the issue, and crush it when they were done. I still have complete faith in my dealership and the service department. Just a 1 in a million fluke I hope. I put 3400 miles on the loaner Edge that I had the entire time mine was at the dealership.

Why did you sell so many parts from the Oxford white Mustang? You mentioned in a thread you had 2 different 2018's why did you get rid of the first one?

 

[ElCid08]

First one was white also. A really early build date 18’. Car had 10R80 trans issues. Ford fixed it, but I had the dealer find me a higher optioned 18’ and I traded the first one. Got a much better financing rate.

 

[Sheenapple]

Fyi if they test the IMRCs in the intake mani it will likely pass. This is because the actuator itself is not damaged nor malfunctioning, but the flap that the actuator controls is broken or stuck. The IMRC actuators control one flap on each side of the intake, each flap covers all of the pistons on that bank. So if you are misfiring on cylinder 4 this would tell me that there is likely a problem with the passenger side IMRC flap, since piston 4 is on the passenger side by the back of the firewall. Similarly so if the driver side flap was broken it would misfire cylinder 8, which is also at the back of the firewall, but on the driver side. The driver side flap failure is the most common, but it’s the same piece of garbage on the passenger side as well.

Based on my experience, if you put in a new coil pack, new spark plug (and gapped it properly) then replacing or at least pulling the intake off and holding it in your hands is next. Other serious things could be something wrong with the head, or head gasket or something going on in the cylinder. Compression check.

They need to physically pull the intake out and manually open and close the IMRCs in addition to confirming the actuators work. This will rule your intake in or out

This is the most common and easiest solution, so give all of this a try before anything else.

 

[Shifting_Gears]

Far out they must be shit mechanics if they can't trace a miss fire.
Seems unbelievable they would buy back a car over something like that

Sometimes I feel like this is how things play out at the dealer:

Customer: My car has a misfire that happens intermittently and causes the check engine light to flash.
Dealer: We will run a series of diagnostic tests to determine the issue.
Customer: Great.
Dealer: Your windshield wipers just needed replacing. Problem solved!
Customer: What...?
Dealer: We couldn’t replicate the issue, therefore it never actually happened to you. By the way, we also noticed signs of modifications. We would like to remind you we will deny any warranty work for modified vehicles.
Customer: My windows are tinted.
Dealership: There’s a strong correlation between Mustang’s with tinted windows and engine failure. Thanks for coming in!

 

[wjfawb0]

My 2015 GT had been throwing codes P0308 and then eventually P0300 and P0308 for almost a year. I don't drive it that much, and it cleared up on it's own. I thought maybe I had the crank position sensor issue, but I decided to dig in and take the intake off to look at the IMRC system. The driver's side (5,6,7,8) shaft was broken just past the mechanism, so the sensor was being rotated, but none of the the flaps were being closed at low rpm under vacuum. I'm waiting on my new intake to come in this week.

Here's a youtube video of the flaps in action with the intake turned upside down. After making the video I pulled the mechanism apart to find the break and learn that the shaft is a square metal rod that apparently can't take the torque of the vacuum mechanism. I'm guessing slamming them closed at throttle lift or slamming them open at throttle tip in is causing the shaft to take a hit. Stops on the vacuum actuator would probably fix that.



A picture of the broken shaft where the vacuum mechanism attaches to the shaft is attached too.

 

[Alej]

I do get some of those issues too. Been a few months now and the dealer is fixing one bolt at a time...

That’s cylinders 5 7 and 8 misfires
Crankshaft position sensor issue
And the last one is torque PCM error.
Quite a few... now this happens during HDPE sessions, it’s rare for them to trigger during normal use.

 

[Stang 19]

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!

Spork: sorry to hear about the misfire issue. I know this may sound odd, but mine had a misfire issue that was finally solved by replacing the belt tensioner. Harmonic frequencies appear to be fooling the overly sensitive sensors/electronics in the new cars. Of course, there was nothing wrong and no real misfire going on, just a bad tensioner. Hope this helps.

 

[Spork3245]

Sometimes I feel like this is how things play out at the dealer:

Customer: My car has a misfire that happens intermittently and causes the check engine light to flash.
Dealer: We will run a series of diagnostic tests to determine the issue.
Customer: Great.
Dealer: Your windshield wipers just needed replacing. Problem solved!
Customer: What...?
Dealer: We couldn’t replicate the issue, therefore it never actually happened to you. By the way, we also noticed signs of modifications. We would like to remind you we will deny any warranty work for modified vehicles.
Customer: My windows are tinted.
Dealership: There’s a strong correlation between Mustang’s with tinted windows and engine failure. Thanks for coming in!

Thankfully they already confirmed that there was definitely a misfire on cylinder 4

They still haven’t called me, I’m going to give it until tomorrow afternoon and then call to see what’s up.

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