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

[Maxpowa]

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.

 

[timboslice]

Might be the evap assembly. Mine did something similar. Have you been following the instructions on the gas cap for filling?

 

[CanadianGuy]

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

 

[Maxpowa]

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.

 

[Maxpowa]

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.

 

[CanadianGuy]

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.

Just stop when the pump clicks off. This car has zero give for topping up the fuel.

 

[CanadianGuy]

Could be bad gas. Recent fill up?

 

[Etyrnus]

Just stop when the pump clicks off. This car has zero give for topping up the fuel.

And wait a few seconds after the pump stops to remove the nozzle.

 

[Maxpowa]

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]

Had similar issue from bad gas. Engine vibrated and rumbled erratically with bouncing rpm until I found good gas.

 

[Maxpowa]

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]

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

 

[Maxpowa]

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

Thanks for the reply. Lesson learned. Will post again if something crops up.

 

[Maxpowa]

Thanks for the reply. Lesson learned. Will post again if something crops up.

Just out of curiosity, at what rpm does the engine normally idle?

 

[BoostBumps]

Just out of curiosity, at what rpm does the engine normally idle?

750rpm (warm)

 

[Zissou]

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.

 

[Maxpowa]

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.

 

[kjohn09e]

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.

 

[STeve]

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]

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.