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Discussion Starter #1 (Edited)
OK, I know this topic has been combed thru more than a few times, but I'm here to see if anyone has any updates on what's going on and here to share my/dealer findings.

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.

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.

I could swear my car drove better for a day or two and then back to the old issue.

At this point I'm taking it back Monday (my understanding they'll have one of the Ford engineers on site) and I'll update on their findings.

Does anyone know what the hell is going on? 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 coming up with multiple misfires.

Just throwing this out there as it's my only theory. What are the chances that it's a fuel pump that was spec'd by Ford at not high enough LPH rating or borderline rating to keep 50psi in the lines and as it "ages" or a bit of fuel filter is clogged up, it's no longer able to keep up the pressure. I'm not a pro at this so this theory needs validation from someone, but it's the only thing I got.

Thanks for your input.
 

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Discussion Starter #2
Ok, so the problem is fixed and I'm replying to my own post for anyone having this problem.

What it ended up being is the upper intake manifold fuel/air ratio flaps. I don't know the exact name of them, but it's the flaps in each runner of the upper intake manifold and they weren't mechanically operating to spec.

The solution was to replace the whole intake manifold. Hopefully this'll help someone.
 

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I am glad that all is well with your GT, but it seems strange that something wrong with the intake manifold would be causing a misfire in only one cylinder. I wonder if there was a small crack or warp right over number 8.
Regardless, yours is running fine again, so all is well.
 

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I recently was running at the drags. Everything was great for a couple days. Then I noticed on the drive down the return road a strange "skipping" like feeling between 1,000 and 2,000 rpm. It still happens to this day. I seem to have lost power in that rpm range, but it doesn't seem to have affected things above that rpm. Interestingly, I'm bringing it in to the dealership Monday.

It seems to have happened when I hit the end of the drags I inadvertently pushed in the clutch and took it out of gear right at the end of the run. Back in the day, doing this could cause an engine to eat a valve. I always leave it in gear and simply let off the gas. I have no idea why I pulled it out of gear so fast (stupidity I guess). I'm wondering if this broke something. My car is not throwing any codes....which is odd. Only thing I did engine related was cat back Borla Attacks. Did a lot to the suspension (virtually nothing is stock)....but I didn't modify anything at all to the engine.

It sounds eerily similar to what you are describing. I'll reply with what I find out.

However, I also have another strange thing that has appeared. The traction control says it turns off when I hit the lever, but all the items related to traction control continue to work.....so something's up. I'm not getting any codes so it's time for the dealership to look. Thank goodness this happened before I put the supercharger on...
 

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OK, I know this topic has been combed thru more than a few times, but I'm here to see if anyone has any updates on what's going on and here to share my/dealer findings.

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.

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.

I could swear my car drove better for a day or two and then back to the old issue.

At this point I'm taking it back Monday (my understanding they'll have one of the Ford engineers on site) and I'll update on their findings.

Does anyone know what the hell is going on? 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 coming up with multiple misfires.

Just throwing this out there as it's my only theory. What are the chances that it's a fuel pump that was spec'd by Ford at not high enough LPH rating or borderline rating to keep 50psi in the lines and as it "ages" or a bit of fuel filter is clogged up, it's no longer able to keep up the pressure. I'm not a pro at this so this theory needs validation from someone, but it's the only thing I got.

Thanks for your input.
I had the same issue at 22k miles on my 2016 GT PP. I got a check engine light, pulled the codes, and it showed multiple misfires on # 2, and # 8. I didn't feel or hear a miss, so I cleared the codes. When it came on for a second time, I took it to the dealer, and they swapped the # 2 plug and cleared the codes. 40 miles later the code was on. I went onto Ford's tech forum, and there was a lot of techs commenting on the intake runners cracking and throwing misfire codes. I had the tech at the dealership look into it, and he pulled the intake for inspection. He found the cracks, and swapped it with a new manifold. My question is whether or not the new manifold is a better design?
 

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The dealership said they had a tech bulletin on this. They "reprogrammed" my PCM and said it was fine. Well...issue is still there. It's probably the intake issue. Since I'm going to put on a supercharger I've decided to let the issue go. The stock intake will be replaced by the Supercharger manifold.

I hate dealerships.
 

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Ok, so the problem is fixed and I'm replying to my own post for anyone having this problem.

What it ended up being is the upper intake manifold fuel/air ratio flaps. I don't know the exact name of them, but it's the flaps in each runner of the upper intake manifold and they weren't mechanically operating to spec.

The solution was to replace the whole intake manifold. Hopefully this'll help someone.
 
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