2015 GT PP Manual Shift with Periodic Torque Loss

[2015MustangGTPP]

I have a 2015 GT Performance Package with manual transmission and have a question. This may only happen on manual transmission cars, I'm not sure.

I'm experiencing what feels like on/off torque loss when I accelerate, especially when the engine is cold. Not during hard acceleration, just with regular driving. I usually drive in sport mode, but can feel it in the other modes as well.

For example, if I keep the gas pedal pressed at the exact same spot while my speed is increasing, it will feel like the car is going at normal acceleration, then it'll lose some power for a second, regain power, lose some power. It feels like torque loss and makes the car jerk so the occupants can feel it.

I've brought it in twice to the dealer for service, but they've told me they can't reproduce it and it's normal behavior for Mustangs.

It happens mostly on a cold engine and I've been told there are security measures to save the engine from hard accelerations when it's cold, but this happens while I'm driving normally.

Anyone else experiencing this too and is it really normal behavior?

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[2015MustangGTPP]

Anyone driving a manual who can chime in with their experience?

 

[HeelToeHero]

That doesn't sound normal. Can you post a video?

 

[ORRadtech]

Really not enough information to make a decent guess.
Does the rpm fluctuate when this happens?
Have you checked for stored codes for things like misfires or lean conditions, etc?
What about fuel pressure, good? Constant?
Maybe check for vacuum leaks too.
How many miles on the clutch?
Does it happen when the car is fully in gear or are you touching the clutch at all?

Based on the little you've said it would seem to me the most obvious explanation would be a misfire but that's strictly a WAG.

 

[DrZed]

Have you tried this with the traction control off?

 

[HeelToeHero]

I guess the other questions are if the car is stock. Any intake modifications or a buggy tune?

 

[opengl]

It happens mostly on a cold engine and I've been told there are security measures to save the engine from hard accelerations when it's cold, but this happens while I'm driving normally.

Unsure about your problem, but this is the dealer blowing smoke up your ass, as they are prone to do when they want you to go away.

 

[2015MustangGTPP]

That doesn't sound normal. Can you post a video?

I think it’s too subtle to be seen on a video, but I can try to get one recorded tomorrow.

Really not enough information to make a decent guess.

All good questions you asked below. Hopefully my answers give better info.

Does the rpm fluctuate when this happens?

When I attempt an even acceleration by keeping the RPM climbing evenly, the RPMs does “stall” for a second before resuming the RPM climb. This happens a few times in each gear. Amplified by a cold engine and lower gears.

Have you checked for stored codes for things like misfires or lean conditions, etc?

I don’t have a tool to check it with. I assumed the Ford techs would have done it when I went in, but maybe not. Would I go to a place like Autozone and ask to borrow a diagnostics to hook up to the OBD port? And are those fairly straightforward to use, so I would be able to read those codes without being a tech?

What about fuel pressure, good? Constant?
Maybe check for vacuum leaks too.

I haven’t checked the fuel pressure, or vacuum leaks. I‘ve got Ford’s PremiumCare warranty still, so I should be able to take into a garage and have them check it, but they’ve just been sending me on my way the two times I went in for it, and I’m pretty sure they haven’t done much analysis as I never got any paperwork back in it. Can you just go into dealerships and have them check that under warranty usually?

How many miles on the clutch?

21,000 miles and I haven’t driven it hard. It’s not the clutch slipping.

Does it happen when the car is fully in gear or are you touching the clutch at all?

It happens without touching the clutch, the car is fully in gear. I put it into first, release the clutch, accelerate at a steady pace, a little torque loss for a second, torque resumes for a sec, more torque loss, torque resume, clutch pushed in, change to second gear, release clutch. Rinse and repeat.

Based on the little you've said it would seem to me the most obvious explanation would be a misfire but that's strictly a WAG.

A misfire could be due to spark plugs, coil-on plugs and I’m guessing a lot of other reasons? Any good way to find out that I could tell the dealership?

Getting your guys input is helpful, since the dealership tells me it's normal behavior. If it shows out not to be, I have some ammo and reason for going in a third time.

Have you tried this with the traction control off?

Yes, also with the Advance Trac disabled. It feels more pronounced in some modes than others (e.g. in normal mode with traction control I feel it more than in Track mode with Advance Trac off).

I guess the other questions are if the car is stock. Any intake modifications or a buggy tune?

The car is completely stock with no tune or intake mods.

Unsure about your problem, but this is the dealer blowing smoke up your ass, as they are prone to do when they want you to go away.

Yeah, you may be right. I’ve left the car overnight since the issue is mostly felt with a cold engine, and they usually tell me they test drive and couldn’t replicate it, so I just need to come and pick it up. I am pretty sure they didn’t diagnose after the test drive since they chalked it up to normal behavior.

This issue has been bothering me for over a year now, so all inputs are appreciated so I hopefully can get pinpointed what to do.

 

[Shifting_Gears]

When my intake manifold runner control failed I had very similar symptoms. It was most pronounced when the engine was cold but could be felt cold or hot. Wide open throttle it was fine. Part throttle there was constant surging.

I did get a check engine light after a while as misfires were being detected.

Dealer replaced the intake manifold under warranty.

 

[HeelToeHero]

I think it’s too subtle to be seen on a video, but I can try to get one recorded tomorrow.


All good questions you asked below. Hopefully my answers give better info.


When I attempt an even acceleration by keeping the RPM climbing evenly, the RPMs does “stall” for a second before resuming the RPM climb. This happens a few times in each gear. Amplified by a cold engine and lower gears.


I don’t have a tool to check it with. I assumed the Ford techs would have done it when I went in, but maybe not. Would I go to a place like Autozone and ask to borrow a diagnostics to hook up to the OBD port? And are those fairly straightforward to use, so I would be able to read those codes without being a tech?


I haven’t checked the fuel pressure, or vacuum leaks. I‘ve got Ford’s PremiumCare warranty still, so I should be able to take into a garage and have them check it, but they’ve just been sending me on my way the two times I went in for it, and I’m pretty sure they haven’t done much analysis as I never got any paperwork back in it. Can you just go into dealerships and have them check that under warranty usually?


21,000 miles and I haven’t driven it hard. It’s not the clutch slipping.


It happens without touching the clutch, the car is fully in gear. I put it into first, release the clutch, accelerate at a steady pace, a little torque loss for a second, torque resumes for a sec, more torque loss, torque resume, clutch pushed in, change to second gear, release clutch. Rinse and repeat.


A misfire could be due to spark plugs, coil-on plugs and I’m guessing a lot of other reasons? Any good way to find out that I could tell the dealership?

Getting your guys input is helpful, since the dealership tells me it's normal behavior. If it shows out not to be, I have some ammo and reason for going in a third time.


Yes, also with the Advance Trac disabled. It feels more pronounced in some modes than others (e.g. in normal mode with traction control I feel it more than in Track mode with Advance Trac off).


The car is completely stock with no tune or intake mods.


Yeah, you may be right. I’ve left the car overnight since the issue is mostly felt with a cold engine, and they usually tell me they test drive and couldn’t replicate it, so I just need to come and pick it up. I am pretty sure they didn’t diagnose after the test drive since they chalked it up to normal behavior.

This issue has been bothering me for over a year now, so all inputs are appreciated so I hopefully can get pinpointed what to do.

Really doesn't sound normal. Maybe try a different dealer? Can you request a ride with a technician to show them the symptom?

 

[Bluelightning]

One thing you can do is take it for a drive with the tech that is looking at it, or the service manager, with you driving so that you can replicate the problem for them. Most dealers are open to doing this for you.

 

[2015MustangGTPP]

When my intake manifold runner control failed I had very similar symptoms. It was most pronounced when the engine was cold but could be felt cold or hot. Wide open throttle it was fine. Part throttle there was constant surging.

I did get a check engine light after a while as misfires were being detected.

Dealer replaced the intake manifold under warranty.

That's good to know. I'll definitely keep that in mind and mention it on my next service appt. WOT is fine in mine as well.

Really doesn't sound normal. Maybe try a different dealer? Can you request a ride with a technician to show them the symptom?

I probably have to go somewhere else. Unfortunately there aren't many around here, but it's probably my best option. I'll request a technician to go with me next time as it's a lot easier to replicate when I can explain and demonstrate the issue.

One thing you can do is take it for a drive with the tech that is looking at it, or the service manager, with you driving so that you can replicate the problem for them. Most dealers are open to doing this for you.

Yes, that'll be my next step then. Thank you.

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