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Discussion Starter · #1 ·
Hello all,

For some time my 13 FoST ST2 has been misfiring hard under heavy boost, or basically anytime I’m deeper than halfway into the throttle.

I was running an OTS Cobb Tune for a little (I know don’t hurt me), but have since reverted it back to stock and the problem persists on both.

I started with the spark plugs, bought some pre-gapped to .26 from Panda Motorworks. That didn’t fix it, although two of the electrodes were very off.

This week I finally got a CEL code for the Bank 1 O2 sensor, and since it doubles as the wideband on these cars and helps control AFR, I went ahead and replaced that. No luck there either.

To me the next step would be fueling, except that on my Accessport I can see it isn’t being cut because it’s lean or anything like that. I haven’t gotten any other relatable codes, the only other existing ones right now are for Fan Control Module 1 and the sound symposer Maybe it’s related, so I’ll mention that occasionally if I am sitting at idle it will start to run hot after a while, however I just attribute this to the fan as it’s not leaking coolant. I do know that sometimes the coolant system can cause a car to misfire, but it’s happening regardless of engine temperature.

Any advice would be helpful. I will be running some really good fuel system cleaner through it this week hoping that clears it up, but I am otherwise lost. I don’t have the means to check compression outside of my apartment complex currently. Thanks in advance.
 

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Hello all,

For some time my 13 FoST ST2 has been misfiring hard under heavy boost, or basically anytime I’m deeper than halfway into the throttle.

I was running an OTS Cobb Tune for a little (I know don’t hurt me), but have since reverted it back to stock and the problem persists on both.

I started with the spark plugs, bought some pre-gapped to .26 from Panda Motorworks. That didn’t fix it, although two of the electrodes were very off.

This week I finally got a CEL code for the Bank 1 O2 sensor, and since it doubles as the wideband on these cars and helps control AFR, I went ahead and replaced that. No luck there either.

To me the next step would be fueling, except that on my Accessport I can see it isn’t being cut because it’s lean or anything like that. I haven’t gotten any other relatable codes, the only other existing ones right now are for Fan Control Module 1 and the sound symposer Maybe it’s related, so I’ll mention that occasionally if I am sitting at idle it will start to run hot after a while, however I just attribute this to the fan as it’s not leaking coolant. I do know that sometimes the coolant system can cause a car to misfire, but it’s happening regardless of engine temperature.

Any advice would be helpful. I will be running some really good fuel system cleaner through it this week hoping that clears it up, but I am otherwise lost. I don’t have the means to check compression outside of my apartment complex currently. Thanks in advance.
Did you manually check the gap on the plugs?

What's your AFR?

Do you have any logs?
 

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Discussion Starter · #4 ·
I lazily did not manually check the gap on the plugs because I’ve recently moved and don’t have the means at my apartment complex readily available. I trusted them from the shop, and the old ones were so out of whack too that I thought it could only be better.

AFR reads fairly normal through most pulls, runa more on the rich side when it does get into misfire territory nearing 9-10 range sometimes, which is why I would’ve thought it was the O2 sensor as it’s also part wideband.

I don’t have a log on it yet because I’ve not ever actually had a need for one, but I could log it sometime here soon if it might point me in the right direction. I just wouldn’t know where else to start truthfully with as many things as it tracks.
 

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Discussion Starter · #5 ·
Hoping someone will come back to this, I finally got around to checking the plugs and they all are gapped properly. Additionally, they did not look fouled or at all uneven in terms of timing. Attached is a datalog I just took after putting it all back together. I haven't ever examined one before, but I can't figure out much. I went WOT in third and it misfired like crazy, almost as if it was on two-step. Going to be checking for compression numbers this weekend, but my only other thought is maybe an exhaust leak. It builds boost no problem, and the datalog doesn't indicate any big spikes anywhere that I can see. Any help is much appreciated.

Datalog File Google Drive
 

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Hoping someone will come back to this, I finally got around to checking the plugs and they all are gapped properly. Additionally, they did not look fouled or at all uneven in terms of timing. Attached is a datalog I just took after putting it all back together. I haven't ever examined one before, but I can't figure out much. I went WOT in third and it misfired like crazy, almost as if it was on two-step. Going to be checking for compression numbers this weekend, but my only other thought is maybe an exhaust leak. It builds boost no problem, and the datalog doesn't indicate any big spikes anywhere that I can see. Any help is much appreciated.

Datalog File Google Drive
Can you add the other ign correction cylinders to that? My first thought here is your AFR looks way too lean for 100 pedal position/WOT.
 

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Discussion Starter · #8 · (Edited)
Can you add the other ign correction cylinders to that? My first thought here is your AFR looks way too lean for 100 pedal position/WOT.
Weird that his ignition correction is basically flat zero the whole time.
Here is the updated file. Took me a minute to figure out how to configure the log and then even longer to figure out the maximum number of things I could select. Misfire counter added far right as well, you can see it climb during the pull.

Updated Data Log File
 

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The computer is getting the wrong signals or something is tainting the commands. Like a vacuum leak. But, lets wait for the compression test. You are getting the highest boost with 80’s% pedal position. More than that, the combustion is getting too much air and running slightly on the lean side. Too much air or not enough gas. Fuel pressures needs to be monitored. How many miles? No P300’s codes?
 

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Discussion Starter · #13 ·
The computer is getting the wrong signals or something is tainting the commands. Like a vacuum leak. But, lets wait for the compression test. You are getting the highest boost with 80’s% pedal position. More than that, the combustion is getting too much air and running slightly on the lean side. Too much air or not enough gas. Fuel pressures needs to be monitored. How many miles? No P300’s codes?
148k miles. No P300 or any other engine codes, only for the grille shutters and the sound symposer. I did have a code for the fan control module and the bank 1 O2 sensor which is the wideband one come recently, but both have since been taken care of and not come back. Would an exhaust leak be a possible culprit? This has been a while now acting like this and no codes on the accessport have led to fixing it, I especially thought the O2 sensor would.
 

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Discussion Starter · #14 ·
The computer is getting the wrong signals or something is tainting the commands. Like a vacuum leak. But, lets wait for the compression test. You are getting the highest boost with 80’s% pedal position. More than that, the combustion is getting too much air and running slightly on the lean side. Too much air or not enough gas. Fuel pressures needs to be monitored. How many miles? No P300’s codes?
Went out and took another log with a few different measurements, are these along the lines of what we are looking for? If not, what should I be logging? The number of terms is beyond me.
 

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Here is the updated file. Took me a minute to figure out how to configure the log and then even longer to figure out the maximum number of things I could select. Misfire counter added far right as well, you can see it climb during the pull.

Updated Data Log File
Your AFR is way too lean for WOT, highest safe range should be like 11.91 with pedal at 100. Ideally, lower. AFR in mid 12's at WOT Is starving your engine.

Other thing, you have some serious negative corrections. -4.5 in Cyl 2 is bad. That's inducing some heavy knock, prob the misfires too.
 

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Discussion Starter · #17 · (Edited)
Your AFR is way too lean for WOT, highest safe range should be like 11.91 with pedal at 100. Ideally, lower. AFR in mid 12's at WOT Is starving your engine.

Other thing, you have some serious negative corrections. -4.5 in Cyl 2 is bad. That's inducing some heavy knock, prob the misfires too.
Had you noticed an exhaust leak? Get it compression tested. It’s running too lean, can damage the engine.
I realize I forgot to include the latest datalog with the added fuel numbers. That is below now. Looked more specifically into Cyls 2 and 4 as those were the ones that had the poor timing adjustment, but still unsure if these are the right things to be looking at for logging. It is hard to say on an exhaust leak, but I think I may have one. I'll be getting underneath it sometime here in the next week or so. It is lowered and I live at an apartment complex so I have to wait on the logistical stuff for that to be available. I will be compression testing it this weekend with a rented tool from Autozone or somewhere and looking more for inconsistency than a perfect number. Any other advice?

I'd like to note I don't normally drive it like this. At most when daily driving, because I keep it under control, the worst I will get is one or two noticeable misfires. It is really only if I bury my foot, which I do for the purpose of the log at WOT.

Log with Some Fuel Numbers
 

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Discussion Starter · #20 ·
Had you changed the purge valve? The symposer sometimes get bad and play games with the vacuum/boost due to leaks.
Fuel pressure is taking a dip after 4135 rpm. Purge valve?
It hasn't ever been changed out to my knowledge. Would it be possible for it to be bad and not trigger a code? The symposer code is P26DE, which I would think is unrelated.

The car was a lease vehicle -26k miles, then bought by the parts manager at that Ford dealership, then sold to me by that guy at 119k so it was always well taken care of.
 
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