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Discussion Starter · #1 ·
Hello,

I purchased my 2016 Focus ST (ST2) in August of 2016. The vehicle now has 11k miles after about 11 months of ownership. In the first 2k miles of owning the vehicle i began to notice a drastic acceleration issue that would occur once every few starts sometime more often and other times less its very off and on but has continued to happen even now. The acceleration issue occurs when the vehicle is started after sitting and cooling down for a while and after running it and then starting it again while its still warm.

The acceleration issue is odd and i have never heard of or experienced it in any other vehicle before.
Though the issue does not always occur, when it does it is immediately felt in the way the car accelerates. After starting the vehicle at slow speeds (0-15mph) the acceleration of the car feels normal. But once you hit half throttle in and gear under 5th the acceleration becomes sluggish and you can feel the car struggling to accelerate. The acceleration feels half as strong as when the vehicle is properly functioning. When the throttle is floored in 3rd the Focus ST will not rev past 4k on the tachometer. In 3rd gear with the throttle to the floor the car feels like full throttle in 6th gear with very little acceleration and the car struggling to accelerate. The weirdest part is that in 3rd gear at 3k rpms the boost gauge jumps right to full boast on the indicator on the dash but there is no boast felt in the car. Normally the car gradually starts to build boast at 3k rpms, but with the acceleration issue it instead jumps right to full boast with no feeling of boast building at all.
1st and 2nd gear don't struggle as much as 3rd gear when accelerating but both gear still don't rev even near to red line they peak 2-3k rpm below red line even at full throttle. There the same issue with boast in all gear as there is in 3rd the display reads full boast instantly at 3k rpms but no boast is occurring.
The issue will keep occuring as long as the vehicle is left on. But if the car is restarted the issue always goes away and the car is back to normal function and acceleration.

The acceleration issue concerns me because the car is not even a year old and it keeps occurring every few starts. I don't want to leave it unchecked and get out of warranty and find out the car is a lemon and there is a bad computer glitch or something. I have brought the vehicle to a dealer at around 8k miles and they could not find anything wrong with the car mechanically while they had it but the issue doesn't occur every time it starts.

I have come to the forums looking for advice and suggestions on what to do next. I am also curious if anyone else had similar issues with there vehicles which i have so far not seen on this forum. Any help would be greatly appreciated. Thank you for your time.
 

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Mine did that once a couple of weeks ago, but only the one time.

It was pretty much exactly as you describe. I also thought I heard what might have been air escaping like a boost leak or something but I am not sure.

There were also no codes and no lights on the dash.
 

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Discussion Starter · #5 ·
There are no codes popping up at all. And when i took the car to the dealer they couldn't find anything wrong with the car. I think what is happening is the turbo is just not spooling for some reason but when the car is restarted after the issue happens the car is back to normal. And there are no leaks or issues mechanically im thinking since once the car restarts everything is back to normal with full power. I am thinking its possible a computer glitch which i don't know what to do about and its weird that it keeps happening every few starts and isn't a one time thing.
 

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A few Questions:

What Octane fuel are you running?
What fuel level does the issue occur at?
Has it ever occurred on a full tank?
How many tanks of gas has this occurred on? Was the fuel from different sources?
What part of the world do you drive in?
What has the weather been like lately?
Any mods on the car?
 

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Discussion Starter · #7 ·
A few Questions:

What Octane fuel are you running?
What fuel level does the issue occur at?
Has it ever occurred on a full tank?
How many tanks of gas has this occurred on? Was the fuel from different sources?
What part of the world do you drive in?
What has the weather been like lately?
Any mods on the car?
I have always run 93 octane fuel from a few gas stations in my area and have consistently had the acceleration issue arise. The issue has occurred on a full tank it happened just the other day. The issue has occurs a few times for every tank of gas i go through. I live in the south east united states for its hot a humid. I have a roush intake and cat-back exhaust both installed by a ford dealer.
These are good things to look at i agree but the weirdest thing about the issue is if the car is restarted once you notice the issue its back to normal every time. The ford dealer i took it to couldn't find any issues with the car but im not surprised its off and on but common.
Thank you for your time and any advice would be greatly appreciated.
 

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This sounds really similar to what I experienced for the first time today... I thought my clutch is going (it may be the clutch I dont know)

But just randomly after starting the car again hot, it just failed to accelerate.

Im letting it cool now before I go test run it again.
 

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Could it really be so noticable?

I went from "damn, I broke my car"

To a test drive after cooled down where clutch was gripping well and no noticable acceleratiom issues
Well stock fmic heatsoaks after one pull. Large power loss. Lack of ignition advance from increased cylinder temps. It will be sluggish.

Test the clutch on the highway. 5th gear, around 2.5-3k rpms on level-ish ground, floor it. 100percent throttle. If your rpms increase and not your speed you are slipping.

Intermittent slips are harder to diagnose. So this test isnt 100 percent accurate.
 

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I experienced pretty much zero perceptable slip during the hwy Test.
I hate troubleshooting intermittent issues.

Maybe you are driving yourself insane. It could be fine. Unless it has been multiple occurances under the same conditions. Then we know it's a time bomb.
 

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I have always run 93 octane fuel from a few gas stations in my area and have consistently had the acceleration issue arise. The issue has occurred on a full tank it happened just the other day. The issue has occurs a few times for every tank of gas i go through. I live in the south east united states for its hot a humid. I have a roush intake and cat-back exhaust both installed by a ford dealer.
These are good things to look at i agree but the weirdest thing about the issue is if the car is restarted once you notice the issue its back to normal every time. The ford dealer i took it to couldn't find any issues with the car but im not surprised its off and on but common.
Thank you for your time and any advice would be greatly appreciated.
Well the good news is doesn't seem to be fuel related. I would put my money on the engine pulling almost all the boost and timing due to the intake charge being too hot. If you could get something to check Ignition timing, Boost, fuel pressures and post intercooler temp charge temp, you would likely see the engine cut back power to protect itself.
 

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I hate troubleshooting intermittent issues.

Maybe you are driving yourself insane. It could be fine. Unless it has been multiple occurances under the same conditions. Then we know it's a time bomb.
It has only happened this once, I now believe it may have been a boost leak at my symposer delete brought on by all the heat. There was oil on it, and one bolt was 1/4 turn from tight, and the port was about 1.5 turns from tight.

The boost was loud, and sounded louder than normal but I wrote that off to me freaking that my car was dying.

That would definitly cause a higher rev with perceptible acceleration issues, compared to with boost.
 

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Are you hearing any uncommon noises when the issue occurs? Any excessive intake or wooshing of air?

Sounds like a charge pipe could be loose or cracked/broken. This would cause a boost leak which leaves the car basically powerless. Depending on the temp it could be worse at certain times due to it being rubber. There is a charge pipe connected to the manifold, both sides of the intercooler, and the turbo.

When the issue happens does the needle on the boost guage move at all while you press the throttle? I would record the problem in action with that handy smart phone of yours and present this to the dealership on your next visit.

Bottom line is you are covered under warranty. If you are at all uncomfortable looking for the issue yourself, Let those ****ers deal with it until it's fixed right.
 

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Discussion Starter · #19 ·
Are you hearing any uncommon noises when the issue occurs? Any excessive intake or wooshing of air?

Sounds like a charge pipe could be loose or cracked/broken. This would cause a boost leak which leaves the car basically powerless. Depending on the temp it could be worse at certain times due to it being rubber. There is a charge pipe connected to the manifold, both sides of the intercooler, and the turbo.

When the issue happens does the needle on the boost guage move at all while you press the throttle? I would record the problem in action with that handy smart phone of yours and present this to the dealership on your next visit.

Bottom line is you are covered under warranty. If you are at all uncomfortable looking for the issue yourself, Let those ****ers deal with it until it's fixed right.
I took the car in 4 days ago and told them everything that is happening and told them to keep it till they can recreate the issue which shouldnt be hard but idk. Its been 4 days with no updated or info on the issue. I said to keep it till its fixed or they give me other options since its a major issue i dont want to go out of warranty with. It doesnt seem to be a leak since when i restart the car right after it is running fine and full power. And when the issue occurs the boast jumps right to full on the gauge. But no boast is felt and the car is slower than my buddies Kia Soul.....
 

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Could it be that the stock cheesy BOV is failing? I mean it's just a spring and a plate, and a plastic cover. It would explain the massive boost he experienced/heard.
 
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