2015 BRZ - Rough idle + acceleration struggles

[Jfheisenberg]

Originally Posted by FR-S2GT86

I think you're going to have to start posting some data logs for some of the guys on here to see in order to help you out.

I do have some logs i capture with OFT, but i have no idea what im looking at. I will post it here.

Originally Posted by whataboutbob

Any check engine lights? Can you use a scanner to see if there any past/pending codes?

No CEL currently, when i removed the OTF tune before taking it to the dealer, i got a check engine light for P219A (But i think this was because i have a catless header) The light went away after i reflash back to stage 2 OFT

Originally Posted by Thefalls

Did you have a look at your throttle body if its stuck open?

Normally you should have had CEL.

Already remove the throttle body and cleaned it. Before and after doing that, issue is still there. And yes i should get a CEL! very frustrating to know there is a problem but cant figure out where is it.

[Jfheisenberg]

I Uploaded the log file from OFT here https://easyupload.io/js6g2m

Its a CSV file.

[NoHaveMSG]

Originally Posted by Jfheisenberg

I Uploaded the log file from OFT here https://easyupload.io/js6g2m

Its a CSV file.

Can you give some context as to what is happening? Is this a hot idle, cold idle? Looks like you where revving it up some but it is hard to tell what you are doing. I can't tell since you have no injection mode or coolant temp logged. It is also easier to find issues at steady states. Letting it idle and blipping the throttle is hard to read. IE a 30 second hot idle not touching the throttle, or a steady cruise. There is for sure some weird shit going on. That first 4-5 seconds the maf voltage, vacuum, and load barely changes but you are getting large swings in AFR.

[dholloway543]

I was having the same issue, after checking both my o2 sensors and in the process of verifying that the other sensors all worked correctly I unplugged my maf sensor while the car was running and it started idling correctly. This is a sign of a bad maf sensor that needs to be replaced. Now I'm having from finding the issue but sad because toyota wants 200 for a maf sensor. Hope my problems help your problems

[Jfheisenberg]

Originally Posted by NoHaveMSG

Can you give some context as to what is happening? Is this a hot idle, cold idle? Looks like you where revving it up some but it is hard to tell what you are doing. I can't tell since you have no injection mode or coolant temp logged. It is also easier to find issues at steady states. Letting it idle and blipping the throttle is hard to read. IE a 30 second hot idle not touching the throttle, or a steady cruise. There is for sure some weird shit going on. That first 4-5 seconds the maf voltage, vacuum, and load barely changes but you are getting large swings in AFR.

Thanks for looking. The file attached previously was when car was idle and i was revving throughout the RPM band. During idle, i do not notice the sluggish acceleration (obviously lol)

What is happening is the following:

1- When driving the car, i can feel a sluggish/hesitant acceleration. The interesting/weird part is that i can only feel this at around 3k RPM up to 4k RPM. Its possible that the issue is throughout the RPM band, but i can only noticed/feel this problem on such range.

2- The second issue is some rough idle when car is stopped. For this, i have tried to clean the MAF sensor, remove and cleaned the throttle body. It's important to note that this problem got 'better' after i remove my CAI entirely and put my OEM stock box and new air filter.

I have recorded two more logs during driving. (The car was warmed up on both cases) Same .CSV format:

Run 2
Run 3

Originally Posted by dholloway543

I was having the same issue, after checking both my o2 sensors and in the process of verifying that the other sensors all worked correctly I unplugged my maf sensor while the car was running and it started idling correctly. This is a sign of a bad maf sensor that needs to be replaced. Now I'm having from finding the issue but sad because toyota wants 200 for a maf sensor. Hope my problems help your problems

I have not try to unplug the MAF sensor when car is on but i could try it.

What i did try, was to swap my MAF sensor with a friend's MAF sensor (he also has a BRZ), but this didn't make a difference. Unless, i swapped it and forgot to do an extra step that i'm not aware.

[SCFD]

Have you looked into potential fuel pressure issues?

[NoHaveMSG]

Originally Posted by SCFD

Have you looked into potential fuel pressure issues?

Yeah something like that is going on. In the parts of the log where there is a steady idle for 10 sec the AFR is all over the place but maf voltage and load are pretty close to steady.

[Jfheisenberg]

Originally Posted by SCFD

Have you looked into potential fuel pressure issues?

Originally Posted by NoHaveMSG

Yeah something like that is going on. In the parts of the log where there is a steady idle for 10 sec the AFR is all over the place but maf voltage and load are pretty close to steady.

I wouldn't know what to look about fuel pressure.

I do recall that few weeks after this problem started, i borrow my friend's scan tool and it showed a trouble code "P0462 - History - Fuel level sensor 'A' circuit low input". Looks like it was on a history log as i never got a check engine light for this. I mentioned this code to the shop that checked the car and they said it shouldn't be the issue.

Its possible that the issue is related to fuel, but so far the shop i been to were not able to find the problem.

Also, on the OFT i do not have any fault codes or codes shown on history.

[jflogerzi]

Can you do this. Take a log of a few WOT pulls starting around 2500-3K to Redline and post the logs. Use datazapp to view the logs. I am curious through the pull does the car feel sluggish.

What were any changes does to the car prior to it doing this? Whats your IAM at? Any knock in the engine?

[ItsReiko]

Originally Posted by Uncle86

o2 sensor? Or a small exhuast leak? I had the acceleration issues without a cel and found a leak at one of the header gaskets, but that was my issue.

Sent from my Pixel 5 using Tapatalk

Curious how did you find a leak? Do you literally just put your hand near the gasket and feel for air with the car running? I'm suspecting a leak somewhere in my exhaust but don't know the symptoms.

[Uncle86]

Originally Posted by ItsReiko

Curious how did you find a leak? Do you literally just put your hand near the gasket and feel for air with the car running? I'm suspecting a leak somewhere in my exhaust but don't know the symptoms.

I removed my header to find a soot trail leading outward.

Sent from my SM-G781U using Tapatalk

[JIM THEO]

Common symptom when MAF sensor has problem in Subarus.
Cone filters, excessive oil in the filters, vibration etc can cause MAF degradation, try a MAF from a fellow car and see if this is your issue!

[Uncle86]

Originally Posted by Uncle86

I removed my header to find a soot trail leading outward.

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in addition I used the gaskets that came with the headers torqued to spec...when I went OEM "my" issue went away. While I was down there I went ahead and switched out my sensors.

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[Jfheisenberg]

Originally Posted by JIM THEO

Common symptom when MAF sensor has problem in Subarus.
Cone filters, excessive oil in the filters, vibration etc can cause MAF degradation, try a MAF from a fellow car and see if this is your issue!

I tried this already, and didnt make a difference.

Originally Posted by jflogerzi

Can you do this. Take a log of a few WOT pulls starting around 2500-3K to Redline and post the logs. Use datazapp to view the logs. I am curious through the pull does the car feel sluggish.

What were any changes does to the car prior to it doing this? Whats your IAM at? Any knock in the engine?

This is very interesting. I did two hard pulls and on those scenarios, i do not feel the sluggish problem. I am more confused now...

Its possible that the issue is still there, but since i'm accelerating hard i do not notice it on those cases. Seems like the issue is mostly felt when i drive the car 'normaly', when i hit the gas hard, it appears i dont feel the problem.

I did noticed that after driving hard for a bit, my idle problem got a bit worse. It's all strange

That datazap.me tool is great, i was able to upload the two pulls and it shows a graph:

https://datazap.me/u/jframonex/brz-pull-1?log=0&data=1-13

https://datazap.me/u/jframonex/brz-p...og=0&data=1-13

Does this mean anything?