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Erratic Idle, drops/stumbles, then returns to normal.

Messages
173
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28
Location
LA
#1
I have a 2015 with 1600 miles...yes, the damn this is brand new. On my way home tonight, I was sitting at a red light with the clutch in and gear in 1st. I moved the selector to neutral and let the clutch out. The engine idle dropped and the engine felt as though it was going to die. I gave it some gas, the rpm settled and the car began idling fine once more. It happened again, same situation, about 5 minutes later.

I've heard that some Focus ST owners have been having similar issues. Anyone with FiSTs? Any info or insight would be appreciated.

Not sure of this matters: Just before this happened, I filled the car with gas from empty (gas light came on 5 minutes earlier). I use premium all the time from the same company, Chevron.
 


Messages
203
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34
Location
Toronto
#2
Might be the evap assembly. Mine did something similar. Have you been following the instructions on the gas cap for filling?
 


CanadianGuy

4000 Post Club
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Location
Southern Ontario
#3
What mods due you have? For example i had a similar issue with my explorer because i did not wait for the k&n filter to dry a gummed up things. Not saying its that but asking what you done to the car. Also via the accessport( if you have one) you should see some logs
 


OP
Maxpowa
Messages
173
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28
Location
LA
Thread Starter #4
Might be the evap assembly. Mine did something similar. Have you been following the instructions on the gas cap for filling?
Thanks for the reply. I just commented on your post from another thread. I wasnt aware there was any specific process with these cap-less fillers.
 


OP
Maxpowa
Messages
173
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28
Location
LA
Thread Starter #5
What mods due you have? For example i had a similar issue with my explorer because i did not wait for the k&n filter to dry a gummed up things. Not saying its that but asking what you done to the car. Also via the accessport( if you have one) you should see some logs
car is 100% stock.
 


OP
Maxpowa
Messages
173
Likes
28
Location
LA
Thread Starter #9
Just stop when the pump clicks off. This car has zero give for topping up the fuel.
Now that you mention it, I did click it twice. I'll make sure not to top it off and report back next time I fill up or if anything else crops up in the mean time. Thanks for the info everyone. Keep the suggestions coming...
 


XuperXero

Active member
Messages
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124
Location
Wuxi
#10
Had similar issue from bad gas. Engine vibrated and rumbled erratically with bouncing rpm until I found good gas.
 


OP
Maxpowa
Messages
173
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28
Location
LA
Thread Starter #11
Had similar issue from bad gas. Engine vibrated and rumbled erratically with bouncing rpm until I found good gas.
Not sure. Could be. I've come to this station before without problems. I think the overfilling could be the culprit. New to this whole capless filler thing. I've driven the car today with no problems. What exactly happens when I overfill? Could I have caused damage to something?
 


J2FoRS

Senior Member
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Location
Central
#12
Not sure. Could be. I've come to this station before without problems. I think the overfilling could be the culprit. New to this whole capless filler thing. I've driven the car today with no problems. What exactly happens when I overfill? Could I have caused damage to something?
I doubt you could have caused permanent damage since its so new youve likely not forced this condition that many times But you COULD damage the EVAP system by "topping off" which essentially floods it with gas. This would cause the engine to possible stutter and then recover. The EVAP would purge the extra "top off" gas from the carbon canister and the O2 senser reads that the condition is rich and adjusts.

I wouldn't be overely concerned, just stop overfilling now :p
 


OP
Maxpowa
Messages
173
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28
Location
LA
Thread Starter #13
I doubt you could have caused permanent damage since its so new youve likely not forced this condition that many times But you COULD damage the EVAP system by "topping off" which essentially floods it with gas. This would cause the engine to possible stutter and then recover. The EVAP would purge the extra "top off" gas from the carbon canister and the O2 senser reads that the condition is rich and adjusts.

I wouldn't be overely concerned, just stop overfilling now :p
Thanks for the reply. Lesson learned. Will post again if something crops up.
 


Zissou

Active member
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137
Location
Charlottesville
#16
Yup mine have done this a few times and it's always been right after fill ups. The engine speed would dip down while idling at the gas station. The engine even stalled once because of it.

The evap 100% makes sense; same thing happens on Ducati Monsters (very little tolerance for this too, though fueling bikes is a little different since you can't just let the pump click off). On that I just removed the evap canister (very common mod on the Monsters), though that's pretty easy to do on the bike since it's mostly exposed.

I'll refrain topping off the Fiesta's tank and see how that goes. Let us know what that yields for you.
 


OP
Maxpowa
Messages
173
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28
Location
LA
Thread Starter #17
Yup mine have done this a few times and it's always been right after fill ups. The engine speed would dip down while idling at the gas station. The engine even stalled once because of it.

The evap 100% makes sense; same thing happens on Ducati Monsters (very little tolerance for this too, though fueling bikes is a little different since you can't just let the pump click off). On that I just removed the evap canister (very common mod on the Monsters), though that's pretty easy to do on the bike since it's mostly exposed.

I'll refrain topping off the Fiesta's tank and see how that goes. Let us know what that yields for you.
Thanks for the reply. Two days now and car has been running fine. I'll let you know what happens during the next fill up.
 


Messages
176
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31
Location
Fayetteville
#18
I tried topping mine off once. Rounding it off to the nearest dollar. Might as well just sprayed it on the ground. Never had the engine shudder like that though.
 


Messages
160
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28
Location
Simi Valley
#19
I tried topping mine off once. Rounding it off to the nearest dollar. Might as well just sprayed it on the ground. Never had the engine shudder like that though.
Exactly there is a overflow to keep the evap from getting saturated.
 


PhoenixM3

Senior Member
Messages
806
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510
Location
Colorado Springs
#20
Exactly there is a overflow to keep the evap from getting saturated.
Yes, and sometimes that overflow gets blocked by debris, spiders, etc... On our '12 Fiesta SES, the dealer systematically replaced everything in the evap system and eventually the fuel tank. The car was brought to the dealer because the tank was extremely slow to fuel. I was fortunate to be state side at the time. I'm back in Italy now, and dread the thought of having any problem with the FiST which would require a trip to the dealer. Even though we've been in Italy for awhile, I work with Americans, so my Italian language skill is more of a "food menu fluent" vice, technical auto discussion fluent.
 




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