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Old 12-22-2014, 06:05 PM   #1
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Random misfiring

My engine has been misfiring for about 3-4 weeks now. I have Longtube headers, catted x pipe, and Bama tunes. Longtubes have been on my car for about 3 months. When I installed them, engine ran perfectly fine. I have contacted bama, they have made two revised tunes for me, one of them was made off of a datalog. After I installed the tune based off of my datalog, my check engine light turned off and the issue seemed to have been solved. Unfortunately my check engine light has come on yet again.. But the odd thing about this issue is that my engine only misfires during idle, but not ever idle. It usually misfires after the engine has become warm, but like I said it does not always misfire.. I went out and purchased some carb cleaner and sprayed the vacuum lines on each end, yet that didnt never led me to a vacuum leak. At this point I am out of ideas, does anyone have any suggestions for me?

Here is a link of the misfiring:

http://youtu.be/GYnEIww10Ao
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Old 12-22-2014, 11:34 PM   #2
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It's things like this that make me not get a tune. I'm not saying that's what's causing this, but I can see the battle now with my over an issue like this. Good luck with this...
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Old 12-23-2014, 12:02 AM   #3
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It's not the tune, I've had the tune long before I installed long tubes. I was sketched out before I got my tune, but Bama is great with customer service. They also make great tunes!


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Old 12-23-2014, 08:32 AM   #4
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1. An easier way to check for vacuum leaks is just to take a datalog - just turn the logger on when the car is idleing and monitor Short Term fuel trims - Excessively positive indicates a leak.

2. Do you have an oil separator / How many miles on the car?

3. Factory plugs? Again, how many miles?

9/10 times misfires are mechanical in nature, very rarely are they a result of the tune.
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Old 12-23-2014, 08:47 AM   #5
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Originally Posted by 3.7L View Post
It's not the tune, I've had the tune long before I installed long tubes. I was sketched out before I got my tune, but Bama is great with customer service. They also make great tunes!
Hey 3.7-Sorry to hear about the persistent trouble you're running into here. Have you had this looked at locally at all to see if you can get another opinion on this? I'll make sure to pass your comments over to the Bama team as well!

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Originally Posted by Voltwings View Post
1. An easier way to check for vacuum leaks is just to take a datalog - just turn the logger on when the car is idleing and monitor Short Term fuel trims - Excessively positive indicates a leak.

2. Do you have an oil separator / How many miles on the car?

3. Factory plugs? Again, how many miles?

9/10 times misfires are mechanical in nature, very rarely are they a result of the tune.
^Volt to the rescue again and this is exactly what I would recommend doing as well. Keep us in the loop!
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Old 12-23-2014, 09:07 AM   #6
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Old 12-23-2014, 09:15 AM   #7
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Was the transmission removed for any reason?

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Old 12-23-2014, 09:33 AM   #8
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^^ Oh, are you thinking the neutral profile relearn? Completely Forgot about that.
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Old 12-23-2014, 09:39 AM   #9
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^ yes

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Old 12-23-2014, 10:19 AM   #10
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Quote:
Originally Posted by Voltwings View Post
1. An easier way to check for vacuum leaks is just to take a datalog - just turn the logger on when the car is idleing and monitor Short Term fuel trims - Excessively positive indicates a leak.

2. Do you have an oil separator / How many miles on the car?

3. Factory plugs? Again, how many miles?

9/10 times misfires are mechanical in nature, very rarely are they a result of the tune.

1. I'll check that out sometime today, that will save a lot of my time, thanks!2. I do not have an oil separated, I have 17.8k on the car
3. Yes, factory plugs

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Originally Posted by AMAlexLazarus View Post
Hey 3.7-Sorry to hear about the persistent trouble you're running into here. Have you had this looked at locally at all to see if you can get another opinion on this? I'll make sure to pass your comments over to the Bama team as well!



^Volt to the rescue again and this is exactly what I would recommend doing as well. Keep us in the loop!

I haven't had much input other than Bama and my friends dad who is a mechanic. All he did was confirm that it was misfiring, he's too busy to help me out at this time unfortunately.

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Was the transmission removed for any reason?

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Transmission was not removed, only work done on it was a short shifter.



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Old 12-23-2014, 11:07 AM   #11
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Alright I just datalogged the short term fuel trims. I know Volt said overly positive mean that there is a vacuum leak, however I made a video for you guys to help me determine if it is in fact overly positive...

http://youtu.be/arUS-XPs3j8
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Old 12-23-2014, 11:16 AM   #12
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Wow lol... Bank 2 seems damn near perfect. The STFT is the computer adjusting fueling (from the MAF curve) instantaneously in result to engine conditions (for those who dont know). Its viewed as a percentage, <1 being fuel removed, and >1 being fuel added.

Your bank 2 seems to be within +/- 3% on average, which is honestly pretty good. As well as you can expect a remote tuner to get it without spending a SIGNIFICANT amount of time on it.

Bank 1 however is all over the place ... the car clearly doesnt know what it wants to be doing for fueling. STFTs will jump when you're driving due to the inputs being given, throttle position, load, gear ... at idle however they should be stable, and i'm willing to bet your "idle hunting" isnt helping. Was this a cold start, or was the vehicle warm?
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Old 12-23-2014, 11:21 AM   #13
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Originally Posted by Voltwings View Post
Wow lol... Bank 2 seems damn near perfect. The STFT is the computer adjusting fueling (from the MAF curve) instantaneously in result to engine conditions (for those who dont know). Its viewed as a percentage, <1 being fuel removed, and >1 being fuel added.

Your bank 2 seems to be within +/- 3% on average, which is honestly pretty good. As well as you can expect a remote tuner to get it without spending a SIGNIFICANT amount of time on it.

Bank 1 however is all over the place ... the car clearly doesnt know what it wants to be doing for fueling. STFTs will jump when you're driving due to the inputs being given, throttle position, load, gear ... at idle however they should be stable, and i'm willing to bet your "idle hunting" isnt helping. Was this a cold start, or was the vehicle warm?
Car was cold, I let it idle for a minute or two before I recorded the video.
Is there anything I can do to fix the trouble in Bank 1?
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Old 12-23-2014, 11:25 AM   #14
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Well, really not sure what it is to be honest. Could be a faulty O2 (do you have headers?) could just be that the car needs to be fully warm ... really have no idea. You could check the bank 2 plugs and see if they're fouling, incomplete combustion resulting in wacky AFRs could throw the trims off, but thats something i imagine would (should) get caught in a datalog, so i'm kinda just shooting from the hip here.

I think we should go with Rap's original idea though just to get the easy things out of the way first and try an idle relearn. I dont personally know how to do it since i've never had to, but i imagine the procedure is out there somewhere.
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Old 12-23-2014, 11:33 AM   #15
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Originally Posted by Voltwings View Post
Well, really not sure what it is to be honest. Could be a faulty O2 (do you have headers?) could just be that the car needs to be fully warm ... really have no idea. You could check the bank 2 plugs and see if they're fouling, incomplete combustion resulting in wacky AFRs could throw the trims off, but thats something i imagine would (should) get caught in a datalog, so i'm kinda just shooting from the hip here.

I think we should go with Rap's original idea though just to get the easy things out of the way first and try an idle relearn. I dont personally know how to do it since i've never had to, but i imagine the procedure is out there somewhere.
I just went out and warmed the car up until the oil was warm. Same problem occurred, bank 1 was still fluctuating a lot.

I do have long tubes, when I installed them and a tune everything was fine. A few days after I got a check engine light with the code P2254, which relates to one of the rear oxygen sensors. I emailed bama and they sent me a revised tune, I never got that code again. Not sure if this relates to this issue, but I felt it was worth mentioning.

As for an idle relearn, I will take your advice. Time to search google lol.
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Old 12-23-2014, 11:36 AM   #16
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I just went out and warmed the car up until the oil was warm. Same problem occurred, bank 1 was still fluctuating a lot.

I do have long tubes, when I installed them and a tune everything was fine. A few days after I got a check engine light with the code P2254, which relates to one of the rear oxygen sensors. I emailed bama and they sent me a revised tune, I never got that code again. Not sure if this relates to this issue, but I felt it was worth mentioning.

As for an idle relearn, I will take your advice. Time to search google lol.

Good man, lol. Let us know how it goes.
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Old 12-23-2014, 11:49 AM   #17
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I couldn't find anything about an idle relearn for our generation mustang, but in the mean time I will check my oxygen sensors to see if one is loose.


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Old 12-23-2014, 12:03 PM   #18
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Shaun @ AED emailed it to me a while back, i'll see if i can dig it up.
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Old 12-23-2014, 12:07 PM   #19
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Fount it

2011 2012 2013 Ford Mustang GT Idle re-learn instructions - 2011 2012 2013 2014 Ford Mustang GT
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Old 12-23-2014, 12:10 PM   #20
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Thank you so much, I really appreciate it!


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Old 12-23-2014, 12:14 PM   #21
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You got it. Fingers crossed.
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Old 12-23-2014, 01:18 PM   #22
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Alright, so I believe relearning the idle may have solved the random misfiring! After doing the relearning procedure I checked on the short term fuel trims again and bank 1 was much steadier and the car is no longer shaking or making popping sounds at idle. My check engine light is still on, however from my understanding it will take a few days for it to turn itself off, that is if the issue is solved.

I have another video of Bank 1 and Bank 2 to show how steadier it is. I data logged it twice within about 10 minutes of each other, which the video shows.

http://youtu.be/t-y6PFKHWo8
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Old 12-23-2014, 03:36 PM   #23
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Well bad news. Went on another drive today and as soon as I turned the car on it started to misfire again.. Not sure what it could be now


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Old 12-23-2014, 03:39 PM   #24
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Burn it. Claim the insurance.
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Old 12-23-2014, 04:10 PM   #25
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Burn it. Claim the insurance.

Lol not a bad idea...

But seriously does anyone have any more suggestions? Should I start changing spark plugs next?


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Old 12-23-2014, 05:19 PM   #26
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Lol not a bad idea...

But seriously does anyone have any more suggestions? Should I start changing spark plugs next?


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I'm not an expert on your issue, but did you check condition of your spark plugs?

As a far short/last resort, can you switch back to your stock headers and see if it resolves your issue? Provided you don't have to pay anyone to do it for you.
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Old 12-23-2014, 05:42 PM   #27
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I'm not an expert on your issue, but did you check condition of your spark plugs?

As a far short/last resort, can you switch back to your stock headers and see if it resolves your issue? Provided you don't have to pay anyone to do it for you.

I have not check them, I am thinking about buying a new set of spark plugs and installing them.
I don't think the themselves headers are the issue, there are no exhaust leaks and from what I have read exhaust leaks wouldn't contribute to random misfires, although I could be wrong.


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Old 12-23-2014, 06:26 PM   #28
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O2 being bad leads to whacky fueling > Whacky fueling leads to misfires. Thats my guess.
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Old 12-23-2014, 06:36 PM   #29
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O2 being bad leads to whacky fueling > Whacky fueling leads to misfires. Thats my guess.
I was thinking about that too. I found a good deal on Amazon.com for an oxygen sensor, but after looking on AmericaMuscle it appears that the front and rear oxygen sensors are different? Should I purchase a front and a rear sensor and swap them for one of my front and rear sensors and hope that solves the issue?
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Old 12-23-2014, 10:26 PM   #30
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I read a post a while back on another forum with a 3.7 that had very similar symptoms. I tried to find the post again but no luck. However the issue was the crankshaft position sensor. Just a thought.
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Old 12-24-2014, 10:52 AM   #31
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Front o2s measure AFR, rear o2s just measure Cat efficiency and are often times turned off when catless.
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Old 12-24-2014, 12:15 PM   #32
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I read a post a while back on another forum with a 3.7 that had very similar symptoms. I tried to find the post again but no luck. However the issue was the crankshaft position sensor. Just a thought.
Well for my sake I hope new o2 sensors fixes this.

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Front o2s measure AFR, rear o2s just measure Cat efficiency and are often times turned off when catless.
Gotcha. I just ordered 1 rear sensor and 1 front sensor. I should have them in a few days, hopefully this does the job.
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Old 12-30-2014, 02:50 PM   #33
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Just installed a new O2 sensor. The cars idle is much more steady, no random popping at all. Hopefully this is all that it was I still have the check engine light on for the P0300 code, but I am waiting for the car to turn it off itself so that I know the issue is resolved
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Old 12-31-2014, 08:19 AM   #34
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Whew, glad thats over.
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Old 12-31-2014, 12:55 PM   #35
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Glad things are working out. BBK LT's are notorious for O2 sensor issues due to their placement.
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