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Discussion Starter #1
Hi all, having a minor issue with my '14 ST2. I searched the forum and didn't see anyone having the exact same problem I'm having, so I'm reluctantly creating a new thread.

Since I did my latest set of upgrades I'm noticing a problem in the higher gears (4th and up) while the car is under full boost. It feels like a misfire as the car sort of 'pops' and briefly stutters while on the loud pedal. The car has a Roush intake, CPE lightweight intercooler, Ford Performance cool plugs, MBRP cat-back and the latest Cobb Stage 2 93oct tune with the intercooler and Stage 2 tune being the latest upgrades. The car doesn't throw any codes, doesn't idle weird, isn't showing any changes in temps/pressures/mpg/throttle response, nothing. I tried cleaning the air sensor in the intake and reflashing the tune, but it hasn't fixed the issue.

Does this sound like a misfire? Is it something stupid like the traction control stepping in?

I'm hoping the collective knowledge of the forum can help point me in the right direction.
 

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Sounds like you are having the same issue I am having with my car . It happened right after traction control testing. Your car is probably running lean too. Even after switching tunes with it turned off, it still happens but not as severe.

What are your LTFT at idle? If you did a log, what was your AFR and boost numbers. Mine have been all out of wack since the addition.

I would not run the car hard until we find the solution . Check your plugs as mine overheated and were gapped. Check compression, mine was 155 across all 4 so wasnt my issue.

I have replacement hpfp and injectors on there way to me to see if mine are failing and thats the issue as that seems popular on our platform but I am also blindly guessing here.
 

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Hi all, having a minor issue with my '14 ST2. I searched the forum and didn't see anyone having the exact same problem I'm having, so I'm reluctantly creating a new thread.

Since I did my latest set of upgrades I'm noticing a problem in the higher gears (4th and up) while the car is under full boost. It feels like a misfire as the car sort of 'pops' and briefly stutters while on the loud pedal. The car has a Roush intake, CPE lightweight intercooler, Ford Performance cool plugs, MBRP cat-back and the latest Cobb Stage 2 93oct tune with the intercooler and Stage 2 tune being the latest upgrades. The car doesn't throw any codes, doesn't idle weird, isn't showing any changes in temps/pressures/mpg/throttle response, nothing. I tried cleaning the air sensor in the intake and reflashing the tune, but it hasn't fixed the issue.

Does this sound like a misfire? Is it something stupid like the traction control stepping in?

I'm hoping the collective knowledge of the forum can help point me in the right direction.
A log would do wonders to see what is going on, because that could be a number of things. But what are Ford Performance cool plugs, Ford doesn't make spark plugs? So I'm assuming you mean the denso ivt24's? In my opinion ( I run those on my BT setup but only because my ivt22 were showing signs of being a little hot). That is too cold of a plug for your current setup and please pull them one by one and check the gap on them.
 
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The way you describe the issue sounds a lot like the issue I've encountered and I resolved it by checking spark plug gap and/or replacing them. Check your plugs like gringoloco has mentioned the plugs may be too cold and you may have fouled them. For reference we basically have the same modifications but I run ITV-22 which is one step colder than stock, your ITV-24's (assuming "Ford Performance cool plugs") are two steps colder. If they are covered in carbon then I'd swap them out with ITV-22's and then recheck them every so often.
 

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Discussion Starter #6 (Edited)
The plugs I have in the car are one step colder NGKs, that's my bad for rushing a post before looking closer at my order history - they've been in the car for a few months so I didn't remember offhand what they were. (These)

I just drove the car and hopefully got some good data, I need to look at it and see what comes up.

I will definitely pull and check the plugs next.

Thanks for the info!

Update for some data numbers:
At idle the LTFT% is 13.28, actual AFR is 14.7, boost was -10.02; at WOT (throttle pos. 100) the boost peaked at 21.55 and AFR was 11.91
 

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So here are all my logs just in case we have the same issue with the TC. Sorry if I am thread jacking.

Here are the notes for my logs.

So the first log is #465 which was my finished GTX2971 tune before any other changes occurred.

Then he added the TC and told me to do a series of 1st and 2nd gear pulls (#495.
He noticed I was going lean and that the boost numbers were creeping too high so he adjusted the tune and told me to do more logs. This time form a stand still at WOT. (#503 and #504) He was happy with the changes.

When I was driving home from doing these pulls I did a highway pull and noticed misfires in 4th and logged them. (#505)

After sending him this log he sent me another revision of 4th gear. I never logged the change but I did use the car several times after that with no misfires. He said if they occurred again to log it and to send them his way. So I may have foolishly assumed the problem was gone but regardless I drove with the tune for about a week with no issues. I even reported back to him about it as I am the first ST he has worked with this new setup. I loved it and I thought it worked great. Then the temperature dropped and then things went south again. I data logged #509 and #510.

At that point I tell him I am done testing it as I don't like how lean my car keeps getting and was worried it did damage. I took the tune off and returned back to the tune in #465 and since then I have not had normal numbers. At first I thought it was bad gas as my LTFT started around 12.5%, after when i first switched back, and slowly were adjusting downward to about 10%. I did a pull to see if my issue was gone and it misfired again. Since then it has done nothing but gone up to where it is now 17.1% and it has stayed for a few days. From my understand this means the car is reading a lean condition is compensating by adding more fuel.

I have zero leaks, plugs have been replaced, replaced o2 sensor for the hell of it because I had an extra. I compression checked and it hasn't budged at all. So now I am guessing it is fueling and waiting on some replacement HPFP and Injectors from a from a low mile wrecked 2016 Focus ST. As well as replacement lines from Ford. So I may be having a bad day but that guy with the other ST must really be beating himself up right about now.

Any comments, questions or concerns would be appreciated.
 

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LTFT seem a little high. I think LTFT and STFT should remain between +- 10% and them added together should be under +-10%. At least that is what I have heard from other people talking about my high fuel trims.
 

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Discussion Starter #9
Alright, plugs have been checked and the gaps were quite a bit off. When I was looking the gap back up I stumbled on something from Stratified saying a misfire under load/boost is common with a plug gap issue, so hopefully that's all it was.

Thanks everyone, I appreciate the help!

Dagger, I hope those new fuel system bits are able to solve your problem. That donor ST may have died for a good cause after all haha.
 

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The plugs I have in the car are one step colder NGKs, that's my bad for rushing a post before looking closer at my order history - they've been in the car for a few months so I didn't remember offhand what they were. (These)

I just drove the car and hopefully got some good data, I need to look at it and see what comes up.

I will definitely pull and check the plugs next.

Thanks for the info!

Update for some data numbers:
At idle the LTFT% is 13.28, actual AFR is 14.7, boost was -10.02; at WOT (throttle pos. 100) the boost peaked at 21.55 and AFR was 11.91
Our cars seem sensitive to plug gap, and the NGKs come gapped fairly wide. Many tuners recommend gapping between 0.026 and 0.028.

Hope that helps,
Mark
 

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Our cars seem sensitive to plug gap, and the NGKs come gapped fairly wide. Many tuners recommend gapping between 0.026 and 0.028.

Hope that helps,
Mark
Yep I was always an NGK guy until this platform, the gap is a lot larger and it's a lot to try to gap down to .028 imho with these. That is why I run the Denso's because they are pretty close in gap and meet the needs for a quality plug in the needed heat range.
 

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Yep I was always an NGK guy until this platform, the gap is a lot larger and it's a lot to try to gap down to .028 imho with these. That is why I run the Denso's because they are pretty close in gap and meet the needs for a quality plug in the needed heat range.
Funny, I used to run Densos, but with Stratified now recommending against Densos due to observed failures, I've switched to NGKs, which is what I ran in the old turbo'd rally car.

I've never had an issue with the Densos myself, but I'm not running a big turbo nor any exhaust/downpipe mods and we have good fresh 93 here in southern Maine now, so not hitting the plugs with anything more than the occasional knock.

All the best,
Mark
 

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I would suggest turning of FFS (Flat Foot Shifting) is you are using a Ap v3. I had the same issue and had removed the spring on the clutch pedal for better feel. What was happening was once I hot the threshold for FFS, which is usually around 6000 rpms, the car would sputter because it thought the clutch pedal was being engaged. Once my tuner shut it off, everything went back to normal. Also, on the issue with the temps dropping, its probably from your MAP pressure going over 40. Most tunes are set for 40 as a limit and it will stutter once it hits that number an bounces above and below 40. Just a few things that were not mentioned that could be the culprit as well.
 
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