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Car Stalling or "Stuttering" when Idle

Messages
25
Likes
4
Location
Bradenton, FL, USA
#1
Hi,

I drive a 2017 Fiesta ST. It has 5K miles (and change) on it. Custom e-tuned by Jason @ Dizzy.
Mods:
  • COBB FMIC and Piping Kit
  • COBB High Flow Air Filter
  • COBB RMM
  • Whoosh Hybrid Turbo
  • Whoosh Catless Downpipe
  • Flowmaster American Thunder Catback Exhaust
  • Mountune Sound Symposer Delete
  • Mountune High Flow Induction Hose
  • NGK Step Colder Plugs (gapped .023)
  • Turbosmart Dual Port Shortie BOV

I haven't had the car for very long (as you can probably tell by mileage). I live in Florida so it takes some heat. The car tends to drop below 600 or 500 RPM and "stutter" or seem like it's about to stall when in idle and then jump back up to it's desired RPM (800-850 range). The car stalled for the first time when I came to a complete stop and pushed the clutch pedal in while in Neutral. It drives fine other than that. I've looked up almost everything from the CPV/fuel feed, bad spark plugs, fuel pressure sensor, etc...

Kinda not sure if taking it to Ford at this point is an option. Really don't want them to blame the bigger turbo or tune or anything like that. All I know is that it's obnoxious and I really would like to get rid of it.
 


PunkST

2000 Post Club
Messages
2,239
Likes
1,413
Location
Menasha
#3
Have you been over filling the fuel tank when you get fuel? There have been repeat issues across the range of cars with the evap system due to overfilling the tank.

Another thing to check is vacuum leaks. They can do some odd stuff. On my old car i had a line tear and for 6 months it idled like it had a big set of cams, lol.
 


Sam4

Senior Member
Messages
834
Likes
654
Location
West Chester, PA, USA
#5
I tried the one-step colder approach (93 tune w/Livernois), and did not like the way the car ran. Back to factory temp and everything is copacetic.
 


Messages
159
Likes
59
Location
Wichita
#8
Dizzy tuning recommends .028 on their website. Agreed, they need opened up.

Sent from my SM-G960U using Tapatalk
 


TyphoonFiST

9000 Post Club
Premium Account
Messages
11,498
Likes
7,986
Location
Rich-fizzield
#13
Do you have a tune or is it stock? If its tuned have the Tuner set the idle higher see if that helps.

Sent from my SM-N950U1 using Tapatalk
 


OP
D
Messages
25
Likes
4
Location
Bradenton, FL, USA
Thread Starter #15
Do you have a tune or is it stock? If its tuned have the Tuner set the idle higher see if that helps.

Sent from my SM-N950U1 using Tapatalk
He set it to 850. I revert it back to stock tune so I can take it to the dealership on Wednesday. It does it with and without A/C on.
 


Messages
132
Likes
58
Location
Mississauga
#16
Judging by the fact you have a full tank it, I think it is related to the evap/venting for fueling.

I just replaced my evap purge valve hunting down the same issue. On fill ups, even after leaving the filler in for 15-20 seconds after filling, I would get this rich AFR spontaneously at idle and the ecu would overcompensate and make it almost stall.
 


OP
D
Messages
25
Likes
4
Location
Bradenton, FL, USA
Thread Starter #17
Hey guys,

Car does it even when it's 52mi to E / all the time.
I have replaced the Lowside Fuel Pressure Sensor (an issue I read about in the EcoBoost Mustangs), Fuel Rail Pressure Sensor up at the fuel rail, Throttle Body assembly (was wondering if throttle position sensor was glitching), MAF replaced and I've even gone back to stock tune and it still does it. Spark plugs are gapped at .026.

Thinking it is a bad MAP sensor. Any ideas?
 


Intuit

3000 Post Club
Messages
3,603
Likes
2,208
Location
South West Ohio
#19
Car is brand-spanking new. Bad this and that is unlikely. Due to changes, some things are out of parameter, for which the ECU needs to be reprogrammed for. (by qualified personnel who actually know what they're doing)
 


Ford ST

2000 Post Club
Messages
2,921
Likes
3,051
Location
Pleasant Garden
#20
Well you really shouldn't ever run it on the stock tune with an upgraded Turbo.
With all these upgrades that have been done at what point did you start having issues?

Sent from my LG-LS997 using Tapatalk
 




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