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Discussion Starter · #1 ·
Hey guys, I've got a 15 ST MK3 with 44k km on it. I've noticed at idle sometimes the engine shutters almost like a slight miss. Today in the drive through I was watching the tac and it would move about 200-300 rpm up and down from normal idle and I could feel it through the car. Now I have had turbo cars before (96 EVO4) but it didn't do this. Anyone else notice this on theirs? Only mods I have done is sound symposer delete and have only had the car for a month.
 

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Hey guys, I've got a 15 ST MK3 with 44k km on it. I've noticed at idle sometimes the engine shutters almost like a slight miss. Today in the drive through I was watching the tac and it would move about 200-300 rpm up and down from normal idle and I could feel it through the car. Now I have had turbo cars before (96 EVO4) but it didn't do this. Anyone else notice this on theirs? Only mods I have done is sound symposer delete and have only had the car for a month.
Have you checked the spark plugs for wear/gap/carbon build-up?
 

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Discussion Starter · #8 ·
Thank you sir, I shall give this all a read today. Sounds like so far everyones is worse than my issue. Mine is simply a minor rough idle, no stalling. As for bad gas I have removed that because I have gotten premium gas from three different stations to make sure that wasn't it and it still persists. I don't have the sound symposer anymore as I got the Montune delete kit.
 

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Thank you sir, I shall give this all a read today. Sounds like so far everyones is worse than my issue. Mine is simply a minor rough idle, no stalling. As for bad gas I have removed that because I have gotten premium gas from three different stations to make sure that wasn't it and it still persists. I don't have the sound symposer anymore as I got the Montune delete kit.
Btw, I had a 2015 that had a very uneven idle. It was bad enough that it would throw check engine lights for misfires.

Long long long story short, at 17k miles, Ford replaced the cylinder head after they had already replaced all the spark plugs and fuel injectors. After the cylinder head replacement, the idle was even worse and the car continued to throw check engine lights for misfire.
 

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Discussion Starter · #10 ·
Btw, I had a 2015 that had a very uneven idle. It was bad enough that it would throw check engine lights for misfires.

Long long long story short, at 17k miles, Ford replaced the cylinder head after they had already replaced all the spark plugs and fuel injectors. After the cylinder head replacement, the idle was even worse and the car continued to throw check engine lights for misfire.
So theres hope... lol
 

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It could also be something as simple as your upstream O2 sensor. If it is reading wrong or dirty it can cause your AFR to go haywire and screw up your idle. Happened to me personally. It plugs in at the back of the engine sorta toward the driver side. You have to take the wipers and cowl off to get to it, but when I unplugged mine, my idle smooths out so I knew that was the culprit.
 

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It could also be something as simple as your upstream O2 sensor. If it is reading wrong or dirty it can cause your AFR to go haywire and screw up your idle. Happened to me personally. It plugs in at the back of the engine sorta toward the driver side. You have to take the wipers and cowl off to get to it, but when I unplugged mine, my idle smooths out so I knew that was the culprit.
Honest question-

How do you reckon a sensor would be fouled so early in the car's life?
 
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