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2014 GT - P0302 - Cylinder 2 misfiring - need help

24K views 53 replies 17 participants last post by  JBert 
#1 ·
Hi all,

I have a 2014 Mustang GT that I bought in July. It has about 9100 miles on it. I took it out this morning and noticed it was running a bit rough out on the highway. It was shuddering/choppy when accelerating and backfiring when I let off of the accelerator. Turned around and took it straight to my dealership, but they haven't been much help so far.

I have a Steeda CAI, BBK 85mm throttle body, BBK ceramic long tubes, a custom catted H-pipe, and MBRP race series cat-backs on the car, and a Bama tune. The tech at the dealership basically refused to even look at the car with all the after market parts on it, told me he couldn't help me since I wasn't throwing any codes. Suggested I call the place I had the mods done and get them to check it.

On the way home, check engine light came on and the tuner showed it was code P0302, second cylinder misfiring. Turned around and took it back and showed them the code and they still said there was basically nothing they could do, since they don't know if the coil is throwing the code or the after market parts are generating the code and making it look like a misfiring cylinder (if that's the issue, wouldn't checking the coil tell you?).

I still have my factory airbox kit and throttle body, so they asked me to bring those up and let them put those back on the car and test it. Already felt like I was getting hosed and felt even more like it when they quoted me two hours of labor to put the stock parts back on (no way that's a two-hour job. Took about 30 minutes to have it done, initially). Seriously concerned they're going to do the swap, spend a few minutes driving it and tell me they still can't tell what it is because of the headers and exhaust mods and hand me back the car and a $200 bill.

Any thoughts on what the problem may be or how I should approach the dealership?


Thanks,

C-
 
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#2 ·
A little additional info: I've seen code P2626 (O2 Sensor Pumping Current Trim Circuit/Open) intermittently, as well. I know high-flow cats are prone to throw codes, so I wrote it off to that, but am now thinking I should have had it checked. The car started idling hard at startup a few weeks ago. I thought it was the colder weather, but I'm starting to wonder if the O2 sensor is bad. All the symptoms seem to fit bad O2 sensor.
 
#3 ·
It may be worth checking with another dealership just to see if they give you the same line. It sort of seems logical to me that you most likely have a bad coil and I'm not sure on your model but I just changed the number two coil on my son's 2000 gt today along with the plug and with taking the cia off and putting everything back together took about 1/2 hour and 55 bucks.
 
#4 ·
Thanks for the feedback. Coil would make the most sense with a P0302 code. Car is at the dealer now waiting for them to give me a formal estimate on putting the stock air box back on (to make the tech happy). Think I'm going to call first thing Monday morning and tell them I want the cylinder 2 ignition coil replaced before they do anything else; eliminate the most obvious possibility first and go from there, if necessary.
 
#5 ·
I know I'm new to the forum and I don't have an SAE cert but I am a PHD certified Harley tech and I am absolutely appalled at that tech tellin you to put all that back to stock to fix a #2 cyl misfire code!!! If told one of my customers that my boss would have a fit!!!... personally I think you should find another shop cause that guy sounds like a lazy douche!!... and had they nerve to charge you when they didn't fix your problem!... it does sound to me however like you could have either a faulty injector with the mods your talkin about or a bad coil
 
#11 ·
I disagree. A Ford tech shouldn't have to work on a car with all those parts that aren't OEM as well as running a tune. This is where if you mod a car you do so at your own risk which is why Ford as well as other car manufacturers have gotten tougher over the years.
 
#6 ·
Is there any way you could put the stock airbox and tb back on yourself? It would take about 20 minutes and you'd save all that money. Very easy stuff.

Rather than replacing the coil, have them swap it with another one to see if the misfire follows the coil.

How were you driving it when the issue arose? Just cruising along or some highway pulls?
 
#8 ·
I don't believe the TSB applies if there is an actual misfire. I thought it only applied if there was misfire codes without an actual misfire.
 
#9 ·
When I first noticed it this morning I was driving on the highway at about 70-75 MPH. When I let off the gas, the car would backfire a couple of times (which it hadn't been doing), and when I accelerated again it was choppy and uneven. On the way to the dealership, I was noticing it on surface streets as well, going 30-40 MPH.

It is a manual transmission. I'm aware of the TSB, but my car was manufactured past the included date. If the coil isn't the issue, might not be a bad idea to at least call their attention to it.

They haven't charged me to return the air box and throttle body to stock yet. They're supposed to call with an official estimate on Monday (which I'm sure will still be two hours of labor). I'm not a mechanic and I'd prefer to let the experts tackle the air box and throttle body swap if it comes to it. I don't mind paying them to do it, but I will NOT pay for two hours labor for that job and I'll take it to the service manager if I have to. I bought the car there and I am not going to let them job me on labor costs for something that simple.

The coil swap is an excellent idea. Hadn't thought of that, but if the fault follows the swap that would settle it.
 
#13 ·
Diagnosing it yourself would have been easy enough, for the record.

Pull the coil and swap it with another cylinder's. Say cyl #4.

Pull the plug and swap it with a different cylinder, like #6.

Clear the code. If it comes back as either Cyl 4 or Cyl 6, you have your answer.
 
#15 ·
Update: Dealership put a new coil and plug on cylinder 2 and the code switched from P0302 to P0300 (random misfire). Took the car to Dallas Mustang, where I had the mods done. They're data logging it this afternoon, so hopefully I'll know something by tomorrow morning.
 
#16 ·
How was it running when you picked it up from the dealership?
 
#17 ·
Too many mods for Bama canned tune. Im not supprised your car is not running well. Get a custom tune or atleast datalog your car to make sure its running right to begin with (after you figure out what is wrong this time). I inquired about a Bama tune once and asked them if they would allow me to send a data log first before sending me a tune. They informed me they are Pro's and they know how to tune every car for every mod because they have tested it all. I did not know they owned thousands of cars or my car because as far as I always knew every car even in stock form can vary quite a bit to get correct A/F ratios or lambda however you wanna read it. They pretty much refused to let me datalog unless I purchased the tune and it flat out didn't work or left my car on the side of the road. Anything else they must consider success. AM has great customer service. My neighbor actually has a Bama tune and he experianced poor service from them as well and got the same cocky impression from whoever he talked to. He has TB/Intake/headers/catback and after his header install they sent him a tune that almost immobolized his car and it ran very poorly. Im sure if he kept running it that way it would eventually break something. After a few back and forth's with Bama they somehow got him a tune that atleast functioned so he could drive his car. But they never asked for a datalog. They just kept sending him files untill one worked. I know most of what I am saying is not directly related to the OP but in my own twisted way I'm thinking maybe it is. A bad tune can cause parts to wear/break prematurely. I know OP did not say if Bama looked at his logs and verified tip-top shape prior to this but from previous encounters and discussions with my neighbor I'm guessing most likely not.
 
#21 ·
Uh oh. Good luck.
 
#24 ·
Update: Compression tested fine in all cylinders! That's good news, but the crew at Dallas Mustang is pretty stumped as to what it might be at this point. My car already has the O-ring fix from the TSB, so they don't think the crank position sensor is involved. They're going to text the injectors tomorrow. Prime suspect at this point is the tune, but they're really just guessing right now.

Ruled out: Low compression, bad/dirty throttle body, coils, plugs, vacuum leak, O2 sensor.

Hope they find an answer soon.

C-
 
#25 ·
That's awesome news! Maybe they can spend 20 minutes to put the stock TB and CAI back on and re flash to stock to rule out the tune. I wonder why the tune would run fine up until recently if that's what it ends up being.
 
#26 ·
I wouldt be surprised if its the tune.

PM Matt Honeycutt - he's Zeroaviation on here and let him know your troubles. He can hook you up with a perfectly streetable, yet screaming tune. He's a former Ford calibrator and knows what he's doing.
 
#27 · (Edited)
What doesn't make sense (to me) with the tune being the problem is that it's been on the car for five months. Seems weird that it would suddenly start causing issues.

After talking with the lead tech today, we both realized that the only time the car has thrown CE codes is when it's been running Ford's stock tune. Leads us both to believe it's the CAI, TB, and headers that's causing the car to code in that case. That still doesn't explain why the car is running so poorly, though.

Lead tech still thinks it's the Bama tune I've been running on the car. Dallas Mustang has dynoed a lot of 5.0 GTs and they have previously developed tunes for my headers and CAI. They're going to load those to the car today and see how it runs.

Something else I mentioned that he dismissed: I was busy last week and did something I never do. I let the car run down to almost empty before I filled up (I think the computer showed 4 miles to empty when I pulled in at the gas station). I first noticed a flutter about a mile from the station. but I attributed it to the tank's being so low. It was fine heading home after fill up, then started really acting up the next morning. Makes me wonder if water or sludge got into the fuel line/fuel pump/fuel filter/injectors, but the tech doesn't think there are enough miles on the car for that to be likely.
 
#28 ·
Looks like the cuplrits are a bad BBK 85mm throttle body (though this had previously been ruled out??) and a VERY slowly responding O2 sensor on the driver's side. Dallas Mustang said they put the factory throttle body back on and that cleared up most of the problem. They asked to change out the O2 sensor and I gave them the go-ahead. They're going to test it after change to make sure that fixes the rest of the problem. If it does, I can come pick it up this afternoon! Woot!
 
#30 ·
Here's a thought, just a guess. Since your exhaust is highly customized, maybe one of the cats is marginal due to the failed O2 sensor. A fairly quick test would be to swap sides by moving left-cat to right side, and vice versa. The code should change to the other cylinder set on the other side. This assumes the cats are EZ to get to and will just unbolt. Since they are not stock, it might be worth a shot to see if something changes, at the very least. Very frustrating to have multiple problems concurrently.
 
#36 ·
So you had a Cylinder 2 misfire P0302 (passenger side) with rough running then had random misfire P0300 with rough running and now you no longer have the misfire codes but have rough running with driver side lean? Hmmm. Hopefully you figure it all out soon. This seems to have been quite the headache for you. The problem always seems to be one or two steps ahead of you. I'm curious to know what is causing all of his...as I'm sure you are x1,000. Haha

Maybe I missed it, but what cured your misfire codes?
 
#37 ·
So you had a Cylinder 2 misfire P0302 (passenger side) with rough running then had random misfire P0300 with rough running and now you no longer have the misfire codes but have rough running with driver side lean? Hmmm. Hopefully you figure it all out soon. This seems to have been quite the headache for you. The problem always seems to be one or two steps ahead of you.
The tech at Dallas Mustang said the same thing. He's very frustrated because he thinks he has it figured out, implements a fix, and gets little or no improvement in the problem.

I'm curious to know what is causing all of his...as I'm sure you are x1,000. Haha

Maybe I missed it, but what cured your misfire codes?
The misfire codes only showed up when the stock tune was on the car, so it's likely that was caused by all the mods.

It's been frustrating, but at least they know exactly what the problem is now. I'm sure they'll figure it all out pretty quickly. Only so many things that could cause a lean condition, just have to check them one by one and eliminate them until they find the cause. If I had to guess, I expect I'll get the car back tomorrow or Tuesday.
 
#43 ·
#52 ·
Hi all,

I have a 2014 Mustang GT that I bought in July. It has about 9100 miles on it. I took it out this morning and noticed it was running a bit rough out on the highway. It was shuddering/choppy when accelerating and backfiring when I let off of the accelerator. Turned around and took it straight to my dealership, but they haven't been much help so far.

I have a Steeda CAI, BBK 85mm throttle body, BBK ceramic long tubes, a custom catted H-pipe, and MBRP race series cat-backs on the car, and a Bama tune. The tech at the dealership basically refused to even look at the car with all the after market parts on it, told me he couldn't help me since I wasn't throwing any codes. Suggested I call the place I had the mods done and get them to check it.

On the way home, check engine light came on and the tuner showed it was code P0302, second cylinder misfiring. Turned around and took it back and showed them the code and they still said there was basically nothing they could do, since they don't know if the coil is throwing the code or the after market parts are generating the code and making it look like a misfiring cylinder (if that's the issue, wouldn't checking the coil tell you?).

I still have my factory airbox kit and throttle body, so they asked me to bring those up and let them put those back on the car and test it. Already felt like I was getting hosed and felt even more like it when they quoted me two hours of labor to put the stock parts back on (no way that's a two-hour job. Took about 30 minutes to have it done, initially). Seriously concerned they're going to do the swap, spend a few minutes driving it and tell me they still can't tell what it is because of the headers and exhaust mods and hand me back the car and a $200 bill.

Any thoughts on what the problem may be or how I should approach the dealership?

Thanks,

C-
I`ve got the same thing with the 2014 supercharged(ROUSH) I just replaced the fuel injector (HP)
and the coil,
 
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