2018 GT Surge and Hesitation

[CDM77]

I have a 2018 GT PP1 manual that has some strange problems. First of all I have had some weird clutch shudder issues that Ford has not authorized repairs on yet as the car is too new. They want 1000 miles on it before allowing any inspection or repairs, it has 700. That's fine, but another issue has popped up. This one I believe is engine or electrical. When driving around with the RPM low, usually under 2000 RPM the car will hesitate when giving it gas. For example, when traveling around 25 and speeding up to 45 in third gear the car seems to stumble or hesitate at first then takes off. Does it both when slowly or quickly applying throttle. Doesn't matter what speed or gear, just when it is low RPM. Here is the strange part. I disconnected the battery for a while and tried again. Ran perfectly. No hesitation, no stumble. Car felt great- for a few days and then back to stumbling and hesitation again. I have an appointment with my dealer next week, but I was hoping someone has an idea what could be causing this. I am thinking a sensor is bad or there is an issue with the ECU. Thanks.

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[Condor1970]

Funny I just thought of that (ECU issue) in the other thread.

 

[Turbolag87]

Mine does the same... its actually kinda of annoying.

 

[CDM77]

Mine was so bad on Friday that it stalled on a small hill. Was letting the clutch out to start from the stop sign and it just shuddered and stalled, twice. Let the car roll back to a flat spot and just ran the stop sign. Talk about embarrassing, luckily no one was around. I can't remember the last time I stalled a car.

 

[chocoblox]

I have a 2018 GT PP1 manual that has some strange problems. First of all I have had some weird clutch shudder issues that Ford has not authorized repairs on yet as the car is too new. They want 1000 miles on it before allowing any inspection or repairs, it has 700. That's fine, but another issue has popped up. This one I believe is engine or electrical. When driving around with the RPM low, usually under 2000 RPM the car will hesitate when giving it gas. For example, when traveling around 25 and speeding up to 45 in third gear the car seems to stumble or hesitate at first then takes off. Does it both when slowly or quickly applying throttle. Doesn't matter what speed or gear, just when it is low RPM. Here is the strange part. I disconnected the battery for a while and tried again. Ran perfectly. No hesitation, no stumble. Car felt great- for a few days and then back to stumbling and hesitation again. I have an appointment with my dealer next week, but I was hoping someone has an idea what could be causing this. I am thinking a sensor is bad or there is an issue with the ECU. Thanks.

Does it happen in 5th gear? Mine does this, but only in 5th. It’s like the RPM fluctuates for a second and then continues accelerating smoothly

 

[CDM77]

It happens in all gears. It's at the dealer now and so far they can't find any issues. I'm going there today to ride with a tech to show the problem.

 

[Turbolag87]

Mine does it right when I go to shift and lightly press the gas. It almost feels like it’s bucking then picks it right up. I spoke to Dakota (tuner) he says it’s normal

 

[CDM77]

I just got back from the dealer. Had a tech ride along with me. He doesn't believe it is normal, but will have to contact ford. Could be anything from the pedal assembly to the ecu. It was easy to reproduce for him to see. 35mph in 4th gear and then about 50% throttle. Hesitates and bucks 2 or 3 times before beginning to accelerate. Seems ok at higher rpms, but could be doing it there too.

 

[chocoblox]

I just got back from the dealer. Had a tech ride along with me. He doesn't believe it is normal, but will have to contact ford. Could be anything from the pedal assembly to the ecu. It was easy to reproduce for him to see. 35mph in 4th gear and then about 50% throttle. Hesitates and bucks 2 or 3 times before beginning to accelerate. Seems ok at higher rpms, but could be doing it there too.

Please keep us updated. This is my exact issue and it’s been driving me nuts!

 

[CDM77]

Ford had the tech try another mustang on the lot and it does the same thing. They are calling it a characteristic of this engine. It doesn't like low rpms.

 

[chocoblox]

Got around to uploading a video of my transmission “issue”. Notice how the RPM fluctuates in 5th despite consistent throttle:

 

[mmacoyote]

any mods done does it have Cold air intake?

I have a 2018 GT PP1 manual that has some strange problems. First of all I have had some weird clutch shudder issues that Ford has not authorized repairs on yet as the car is too new. They want 1000 miles on it before allowing any inspection or repairs, it has 700. That's fine, but another issue has popped up. This one I believe is engine or electrical. When driving around with the RPM low, usually under 2000 RPM the car will hesitate when giving it gas. For example, when traveling around 25 and speeding up to 45 in third gear the car seems to stumble or hesitate at first then takes off. Does it both when slowly or quickly applying throttle. Doesn't matter what speed or gear, just when it is low RPM. Here is the strange part. I disconnected the battery for a while and tried again. Ran perfectly. No hesitation, no stumble. Car felt great- for a few days and then back to stumbling and hesitation again. I have an appointment with my dealer next week, but I was hoping someone has an idea what could be causing this. I am thinking a sensor is bad or there is an issue with the ECU. Thanks.

 

[CDM77]

No mods done yet. Ford confirmed that it is normal for the 5.0 and manual trans to hesitate under low RPM. Their "fix" is to downshift to accelerate smoothly under 2k RPM. I asked about possible ECU flash updates and was told there are updates, but Ford will not allow the dealership to update the ECU without definitive cause. Good thing I've got a warranty.

 

[CDM77]

Just pulled my car out of storage and took it for a drive. The surging and hesitation has not changed. I need to keep the RPMs above 2000 to have a smooth acceleration, otherwise is shakes and stutters. Last night it nearly stalled out at a stop sign. I started to pull away from a stop and the throttle did nothing. RPMs dropped and the entire car shook as the car tried to stay running. I gave it a lot of gas and it finally picked back up. I was able to pull away but the car did not feel right. I had to push the pedal much further to get any throttle response. It slowly went back to normal responsiveness. I had this same thing happen last fall, but the car actually died, twice. Dealer could not find anything.

This car has been a problem since the day I brought it home. I honestly don't trust it at all. I don't trust that it won't die on the street so I definitely don't trust it on the track.

So far the car has had to have the roof and rear quarter repainted after I found some shoddy mystery repairs that were done before my dealer got the car. Side quarter glass was replaced after finding it had been installed incorrectly. Stalling issue - dealer found nothing. Surging and hesitation at low RPM - dealer found nothing- ford says it's normal. Clutch issues from day 1. From the time it left the lot it has had a chattering clutch. Tech acknowledges something is wrong, but Ford will not allow repair until it has over 1000 miles on it, which it does now. I have an appointment in about a month for the clutch replacement, but these other problems are really getting to me.

I am going to be contacting my sales guy at my local dealership to talk about trading this one in on a different Mustang.

 

[Cobra Jet]

@CDM77

Have you had your car checked for the following:

1) Throttle Body: I had posted on here in another thread that there was either a SSM or TSB relating to the 2018 S550 5.0 throttle bodies. Apparently early builds had throttle bodies assembled with an incorrect spring, which would affect drivability. The throttle body gets replaced under warranty.

2) IMRC issues - this has plagued the 2015-2017 S550 5.0’s - and again causes drivability issues. I have not heard of 2018/19 5.0 owners having the IMRC issue, BUT that is not to say it can’t or wouldn’t be an issue, since the 2018/19’s still have the IMRC system.

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