2015 Mustang GT PP P0308 P0300 (cylinder 8/multiple cylinders misfire) (SOLVED!!!) - MustangForums.com


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Old 08-03-2017, 01:09 PM   #1  
DmitriK
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Join Date: Aug 2017
Location: FL
Posts: 6
Default 2015 Mustang GT PP P0308 P0300 (cylinder 8/multiple cylinders misfire) (SOLVED!!!)

This is something I wrote up on another forum and decided to share the solution because I did a lot of searching and could not figure out what could be an issue and here's my story. Of course, your issue could be different, but it's a fix that worked for me.

I have no CAI (just K&N filter if anything), no tunes. I have a MBRP exhaust and as far as the engine "sees", that's it. Was driving fine for 20k miles, codes came up solid. At low RPM I can feel the hesitation and vibrations. Did the scan a couple of times, it's either cylinder 8 misfire and/or multiple cylinder misfire codes that are coming up.

It's not gas. I tried a whole barrage of different stations and different octane ratings. This problem has been bothering me for the past 2-3 months. It's not cold weather, I live in FL (hot weather if anything).

I ASSUME it's not coil/spark plug/wire/injector as that's probably the first thing dealer tested and codes are coming up with multiple misfires after all.

Took it to the dealer, they programmed the ECU with some service bulletin that came out. No help, problem came back the same day. Took it back, they called the hot line, kept my car for a week and in the end replaced the crank position sensor.

Finally, they told me Ford engineer would take a look at it and it ended up being the upper intake manifold fuel/air ratio flaps.

The solution was to replace the whole intake manifold. Hopefully this'll help someone. Good luck guys.
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Old 08-23-2017, 10:41 AM   #2  
kawiguy827
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Join Date: Jan 2015
Location: California
Posts: 65
Default

So, it seems that your car and mine are similarly set up. I'm going to keep an eye out for this problem. Thanks for the heads up. I have about 20k miles on the exhaust system, 26k on the car, but no issues as of yet.

Is your MBRP system a race or a street? Not to hijack the thread or anything, but I have the street system, and I'm becoming bored with it. Wondering if yours is louder, and by how much (if, of course, it's the race system.)

Thanks again for the heads up on your build/fix!

-J

Quote:
Originally Posted by DmitriK View Post
This is something I wrote up on another forum and decided to share the solution because I did a lot of searching and could not figure out what could be an issue and here's my story. Of course, your issue could be different, but it's a fix that worked for me.

I have no CAI (just K&N filter if anything), no tunes. I have a MBRP exhaust and as far as the engine "sees", that's it. Was driving fine for 20k miles, codes came up solid. At low RPM I can feel the hesitation and vibrations. Did the scan a couple of times, it's either cylinder 8 misfire and/or multiple cylinder misfire codes that are coming up.

It's not gas. I tried a whole barrage of different stations and different octane ratings. This problem has been bothering me for the past 2-3 months. It's not cold weather, I live in FL (hot weather if anything).

I ASSUME it's not coil/spark plug/wire/injector as that's probably the first thing dealer tested and codes are coming up with multiple misfires after all.

Took it to the dealer, they programmed the ECU with some service bulletin that came out. No help, problem came back the same day. Took it back, they called the hot line, kept my car for a week and in the end replaced the crank position sensor.

Finally, they told me Ford engineer would take a look at it and it ended up being the upper intake manifold fuel/air ratio flaps.

The solution was to replace the whole intake manifold. Hopefully this'll help someone. Good luck guys.
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Old 03-14-2018, 08:51 PM   #3  
PJOD87
 
Join Date: Mar 2018
Location: FL
Posts: 1
Default Same code and Misfire on Cyl 8

I replaced the plug, coil and injector. Problem still exists. CEL still on, ran a test, all cylinders fire but still have the CEL and hesitation between 1800-2000 RPM’s is where it really shows itself. Only things left would be check cylinder compression, or could be air related or harness related. Might be the air intake like you guys talked about. Any help would be appreciated.
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