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Discussion Starter · #1 ·
Please let me know if I’ve put this in the wrong place, I just got a 2017 Focus ST and it’s had a shudder for a bit now. Only during idle, the rpms never actually move so I don’t think it could be a vacuum leak. No codes, doesn’t effect the drive ability of the car at all. I thought it was because the dealership put 87 in it but it does it even when it’s got 93. Is this normal? I can’t seem to find anything anywhere about this, and when I called the dealer the service human basically said come back when it’s warmer if it’s still doing it. Im near DC, it’s not THAT cold.
 

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I currently have 2,300 miles on my 2017 ST and I noticed this a little bit yesterday in Chicago (was pretty cold and snowy). My tach didn't move but it sounded and felt like the idle did drop. Just like you my car had no other issues and drove just the same. I'm wondering if the winter blend of fuel or even just bad gas that caused my issue? I will report back if the issues continue or get worse, but it will take me a while as I only drive 150 miles a month.
 

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Does it happen ANY TIME? or only when the engine is cold.. soon after startup?
(Soon after startup means in the first fifteen minutes after a cold engine, start)

Soon after startup would be pretty common.
All the time would be odd.
 

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Discussion Starter · #5 ·
Does it happen ANY TIME? or only when the engine is cold.. soon after startup?
(Soon after startup means in the first fifteen minutes after a cold engine, start)

Soon after startup would be pretty common.
All the time would be odd.


It happens when it’s warm as well, less noticeable but definitely still there.
 

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What brand pf gasoline do you use?
IMO an issue like that is typically cheap crap gasoline.
The gas has water in it, lower than paid for octane, or just bad in general.
I NEVER use anything except Shell locally, and only the top three Shell. BP or Mobil anywhere I go.
 

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Please let me know if I’ve put this in the wrong place, I just got a 2017 Focus ST and it’s had a shudder for a bit now. Only during idle, the rpms never actually move so I don’t think it could be a vacuum leak. No codes, doesn’t effect the drive ability of the car at all. I thought it was because the dealership put 87 in it but it does it even when it’s got 93. Is this normal? I can’t seem to find anything anywhere about this, and when I called the dealer the service human basically said come back when it’s warmer if it’s still doing it. Im near DC, it’s not THAT cold.
All of our cars will misfire on a cold start and you will probably get some at idle even when the car is warm. It's not that bad, just freaks you out if you don't know about it. Nothing to worry about man, enjoy the car. Has happened on both of my ST's and will happen on all of them.
 
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It happens when it’s warm as well, less noticeable but definitely still there.
To clarify, you shouldn't be getting any misfires at all under throttle, especially when the car is up to op temp.
 

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There is a TSB from Ford for the spark plugs pertaining to this issue. I had this issue on my 16 ST1, but hasn't happened at all on my 16 ST3. I would take out the spark plugs and make sure they're all evenly gaped or just take it to the dealer and get new ones put in on the free.
 

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There is a TSB from Ford for the spark plugs pertaining to this issue. I had this issue on my 16 ST1, but hasn't happened at all on my 16 ST3. I would take out the spark plugs and make sure they're all evenly gaped or just take it to the dealer and get new ones put in on the free.
If you're tuned I highly recommend reaching out to your tuner. Many will suggest throwing a step colder and gapping to .026 per Stratified's spark plug article.
 
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I have a copy of the TSB from Ford that came out mid November of last year, apparently 0.040 is what they are gaping them at to solve the issue.
 

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Discussion Starter · #12 ·
There is a TSB from Ford for the spark plugs pertaining to this issue. I had this issue on my 16 ST1, but hasn't happened at all on my 16 ST3. I would take out the spark plugs and make sure they're all evenly gaped or just take it to the dealer and get new ones put in on the free.
If you're tuned I highly recommend reaching out to your tuner. Many will suggest throwing a step colder and gapping to .026 per Stratified's spark plug article.
.

fully stock, I’m just going to swing by the dealer and see if they have any information. Thanks y’all
 

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My '17 has a slight miss when idling, usually when it's at 750RPM (warm). It's done it since new so I don't really think about it. I may get a set of Accel coil packs and the upgraded Ford plugs this spring.
 
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