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Discussion Starter · #1 · (Edited)
Hi everyone I'm new to this forum but not new to owning Mustang's. I bought a 2014 Mustang GT Six speed track pack with 79K miles about a month ago, and about a week after driving around out of nowhere the engine started running very rough. I decided to change the spark plugs with OEM Motorcraft spark plugs and bought a new OEM Mass air flow sensor, it helped a little but not much. The engine runs like it has a misfire, the idle is very rough, and sometimes I can hear backfiring through the exhaust. There are no codes showing, no vacuum leaks that I can see. Another thing I though I'd mention was when the weather was about 30-40 degrees cooler the engine ran even more rough. Right now I'm at a loss, I've heard many different things, maybe the VCT solenoid, the filter, injectors, ect... I called my local Ford Dealership and will have it in on Monday to get diagnosed, but after reading through many forums I'm afraid the dealer might not be able to locate the issue. I would really appreciate any help with this issue, I've barley even got to enjoy the car :( Oh and the only mods done are cai and borla cat back
 

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Give the dealership a chance. They’ll likely be able to nail it down quickly. It’s the small subtle issues that are hard to diagnose.
 

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Welcome to the forum.
There should definitely be codes being registered if it runs poorly especially as bad as you describe.
 

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yeah I am very surprised there are "no codes showing" -- have you scanned it for codes, or are you just talking about the check engine light?
I'm pretty sure there are many codes that will not trip the CEL but will be shown in a scanner
 
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Discussion Starter · #5 ·
Thanks for welcoming me to the forum! I scanned the car for codes with a scanner and nothing is showing up. The check engine light has not come on yet.

I called the dealership that I bought the car from just to see if they did any work to the car and they said the car came in for a p0019 code and they changed the 02 sensor which fixed the problem. You think there's any correlation to my issue?
 

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The CEL light is not necessary to come on for codes to register. When the CEL light comes on it's usually a more serious issue.
 

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As others have stated it should be throwing codes. To be clear.. it ran perfectly fine for days after purchase?.. then BAM! and is constant now?

My first thoughts are you got bad fuel, or a coil is dropping, but again should throw a code.
Yes diagnosis time, maybe check for good Mustang shops aside from the dealer also.
 

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Discussion Starter · #8 ·
I don't understand it either, I keep checking for codes and nothing. I'm surprised too that there are no codes considering how bad it's running. when I bought the car the engine was running really good, and about a week later I remember starting the car and the idle was rough, then I drove it and was really bad, which caused me to change the spark plugs, buy new MAF sensor, run fuel cleaner, and put 100% gas from a top tier gas station.
 

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You could try the idle relearn, where you disconnect / reconnect the battery and then let it idle a few minutes to relearn the idle, and see if that makes a difference.
 

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Discussion Starter · #10 ·
I'll try the idle relearn and let you know if anything changes. I also checked the primary resistance on the cop's and all 8 ran between .8 and 1.0 Ohms, I tried checking the secondary resistance but I couldn't get a reading.

I have a tuner and have been datalogging if anyone knows how to analyze one to figure out what's going on.
 

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I have a tuner and have been datalogging if anyone knows how to analyze one to figure out what's going on.
Can't help there.. but a thought.. you seem like enough of a car guy that you will likely throw a tune on this car, and they are very much worth it.
If so.. I know Lund is awesome. They would read those datalogs and likely hit you back same afternoon.

In your place, I would personally contact them and say hey.. I want to buy a tune for this car I just bought, but here is what's going on. Before I start running dealer diag or anything curious if I could shoot you the logs and get some input before I put in the tune? I would go ahead and pay for the tune, and they likely would say sure send em and let's look.

If you need them I have emails for Nardi, Dakota, and John Lund Jr. great guys. Just a thought.
 

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yeah datalogs are great if you know what to log, how to read the data, and what to look for . . . personally I do not; so I use "Lito" for remote tuning on my car, he is awesome with the 4.6 3V but I don't think he'll touch a Coyote . . . Lund sounds like a good option, and hopefully they would work with you to make sure you are logging the right things, read the file, and then write the tune to fix it.
 
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Discussion Starter · #13 ·
Can't help there.. but a thought.. you seem like enough of a car guy that you will likely throw a tune on this car, and they are very much worth it.
If so.. I know Lund is awesome. They would read those datalogs and likely hit you back same afternoon.

In your place, I would personally contact them and say hey.. I want to buy a tune for this car I just bought, but here is what's going on. Before I start running dealer diag or anything curious if I could shoot you the logs and get some input before I put in the tune? I would go ahead and pay for the tune, and they likely would say sure send em and let's look.

If you need them I have emails for Nardi, Dakota, and John Lund Jr. great guys. Just a thought.
I appreciate the info, I'll definitely contact them letting them know what the situation is and see if they would do something. Leo41, is there anyway I could get the contact info for anyone of the tuners you mentioned?

So I rented a high end scanner and my car came up with a p0315 code and said that the crank needs to be re learned. I hooked up my tuner sct x4 and did a crank re learn, it didn't help at all. I then unhooked the battery and re hooked the battery and now the cars seems to run a lot better, but still runs a little rough. Anyone have any idea whats going on? I'm lost
 

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Whatever other scanner you were using is useless and I would just toss it.
The P0315 code doesn't state that the crank relearn procedure will fix the problem. That code means that there is a problem in that crank position circuit. The relearn procedure is only one of the possible fixes. It's very possibly a bad crank position sensor or the wiring that goes to it from the PCM.
However, this seems to be a known issue from Ford on 2011-14 Mustangs in general and Ford announced Customer Satisfaction Program 17N01 to deal with this in 2017. This program only applies to CA and OR owners though as their emissions tests will fail with this code stored:
The program covers 2011-’14 Mustang models with both the 3.7L V6 and 5.0L V8 that have code “P0315 Crankshaft Position System Variation Not Learned” set. The solution involves a “scan tool code clear” and a 10-minute test drive. The presence of the code can prevent some owners from passing emissions testing. The new warranty covers the vehicle for 10 years and is transferable.
Your battery disconnect essentially cleared the code but since this is affecting the way the car runs it seems like more than a computer glitch to which the program applies. Check the wiring to the sensor and the pins in the plug/connector for damage or corrosion. If it all looks ok then replace the sensor. There are other possible causes for the code that are rarer.
 

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So I rented a high end scanner and my car came up with a p0315 code and said that the crank needs to be re learned. I hooked up my tuner sct x4 and did a crank re learn, it didn't help at all. I then unhooked the battery and re hooked the battery and now the cars seems to run a lot better, but still runs a little rough. Anyone have any idea whats going on? I'm lost
Does the high end scanner have live data? It's like data logging, but looks at virtually every piece of data being electrically transmitted, for any part of the ECM (or any other module in the car besides the ECM).
 

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Discussion Starter · #17 ·
Does the high end scanner have live data? It's like data logging, but looks at virtually every piece of data being electrically transmitted, for any part of the ECM (or any other module in the car besides the ECM).
I don't know cause I returned it to the auto store since my cars at the Ford service center right now, but I bought a new one that does datalog and hoping to plug it in as soon as I get my car back. I just can't believe how long its taking them to diagnose my car, I scheduled and appointment two weeks ago and they told me they would have it diagnosed in two days and fixed a day to two after that. I dropped it off Monday Morning and now it's Friday morning and all I heard is they are still working on it. I'm just fed up with auto shops, they lie all the time.

Whatever other scanner you were using is useless and I would just toss it.
The P0315 code doesn't state that the crank relearn procedure will fix the problem. That code means that there is a problem in that crank position circuit. The relearn procedure is only one of the possible fixes. It's very possibly a bad crank position sensor or the wiring that goes to it from the PCM.
However, this seems to be a known issue from Ford on 2011-14 Mustangs in general and Ford announced Customer Satisfaction Program 17N01 to deal with this in 2017. This program only applies to CA and OR owners though as their emissions tests will fail with this code stored:
The program covers 2011-’14 Mustang models with both the 3.7L V6 and 5.0L V8 that have code “P0315 Crankshaft Position System Variation Not Learned” set. The solution involves a “scan tool code clear” and a 10-minute test drive. The presence of the code can prevent some owners from passing emissions testing. The new warranty covers the vehicle for 10 years and is transferable.
Your battery disconnect essentially cleared the code but since this is affecting the way the car runs it seems like more than a computer glitch to which the program applies. Check the wiring to the sensor and the pins in the plug/connector for damage or corrosion. If it all looks ok then replace the sensor. There are other possible causes for the code that are rarer.
So I did replace the crank position sensor and then unplugged the battery, but then it started running rough again. when I accelerate its like it gets caught up especially around 2k to 3k under light to medium throttle, I also checked the wiring to the crank sensor with a multimeter which was in parameters. I appreciate the info, KEEP IT COMING !!!! CJ67

what do you guys think about a bad PCM?

I got the car back today from the Ford dealership, they couldn't find the problem. They said it could be that the cai or the cat back exhaust, or a tune could be on the car and be causing the issues. Right now there are not tunes on the car, and I don't see how a cai or mufflers could cause such issues. For some reason they also said they could find the P0315 code. I think they didn't really do anything to my car. So anyone have a idea what the heck is going on??????
 

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I'm confused with what your dealer said. They said there MAY be a tune on the car? They would know in less than a minute after hooking it up if there was a tune on the car or not and they can even tell if there ever was a tune in the past which was then restored with the factory tune.
I would suspect the same thing as you. They may have let the car just sit there and then charged you for a diagnostic fee. My dealer won't charge me anything if they can't find the problem which has happened once before but it was an intermittent issue that wasn't acting up when they had it.
they also said they could find the P0315 code
Did you actually mean they couldn't find the P0315 code? Did they provide you with a printout of the scan results or any proof that they did something?
 

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back to basics:

no, "cat back" would not cause a problem and does not require a tune; assuming you mean pipes and muffers and the catalytic converters and O2 sensors are still intact

yes, a CAI will make the car run bad, if it needs a tune but the car is not tuned for it . . . so it is key to find out what kind of CAI you have; does it require a tune; and is the car tuned for it

the dealer can tell if the ECU has been "flashed" aka "tuned" but in my experience they cannot tell what was done in the tune, meaning they can't tell if it was correctly tuned for that CAI

I have a feeling there might be more to the story; like if the car was flashed back to stock somewhere along the way, but it needed the custom tune that it had previously to run right with the CAI, that might explain it
 

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What's key is finding out if a tune is on the car or if there ever has been. The dealer supposedly told him that they don't know if there's a tune on the car(that would be impossible for them to not know if they had it hooked up to their diagnostics) but the OP says there is no tune on the car. So, which is it, tune or no tune, and how do we know that?

The CAI in it can be dealt with by either getting a tuner and custom tune for the car or dyno tune to adjust for it. The less desirable option is putting an original air box back in the car and reflashing the car with the original stock tune provided by a dependable Ford dealer. The OP might need to get a stock reflash by a dealer anyway if it currently has a tune since it runs poorly with whatever might be loaded on there. It's my understanding that a new tune would need to be loaded on top of a factory one.
 
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