Howdy,
I'm going to try and be detailed about this to try and make it informative and maybe make it useful to those getting the same symptoms. I know there are a few threads covering similar symptoms but I'll try and detail new ground if I can. Any insights on things I'm missing or overlooking would be appreciated.
Relevant information:
-2013 BRZ, 84000km, MT
-Injen Intake (earlier)/stock intake (now)
-PLM UL headers
-PLM overpipe
-Invidia front pipe
-Invidia N1
-OFT
Bought in January this year, this was the cheapest BRZ/FRS available near me at the time. It was a rebuilt title due to front end collision and came with the modifications listed above. I purchased this as a project and to use primarily as a track car with occasional Sunday driving (my GTI is a bone stock and very comfortable daily driver). I have only started driving/troubleshooting this past month.
The problem:
From the first test drive, there was a hesitation on throttle most noticable from idle. Recently I have also determined that it something that gets worse as the car warms up. When cold, if you rev the engine the response is snappy, as it should be. When the car is warm it takes a second for the revs to pick up at all, even though the throttle body is opening up. The sound is similar to if you were to make a revving sound with your mouth but took a sharp inhale first. It also shows up when shifting, but is not as noticable.
Here are a couple of crappy videos that may not provide any insight.
Response from idle when cold
Response from idle when warm
I started looking into this problem and found the following resources on this forum (no shortage of good information here!):
High negative STFT and LTFT
https://www.ft86club.com/forums/showthread.php?t=127265
High Negative LTFT on N/A BRZ causing idling issues
https://www.ft86club.com/forums/showthread.php?t=106123
High negative LTFT OFT Stg1 tune
https://www.ft86club.com/forums/showthread.php?t=129889
Throttle Delay Fix.
https://www.ft86club.com/forums/showthread.php?t=115282
MAF Scaling - Open/Closed Loop Fueling info
https://www.ft86club.com/forums/showthread.php?t=64790
OFT - Guide To Dialling In Your OTS Base Tune
https://www.ft86club.com/forums/showthread.php?t=94822
Diagnosis:
After having done some reading I flashed the car with Stg-2-Plus-v4.03 OFT tune and proceeded to drive 3-400km. I started taking data logs to see if I could identify anything that stood out from a "healthy" data log (from Wayno's guide above). A full throttle pull showed nothing seriously wrong but at idle or coasting off throttle the LTFT would sit around -25%. By my observation it seems like in low load or low rpm situations, there isn't proper combustion due to either insufficient spark, unatomized fuel mixture or sensors (MAF/O2) giving improper readings to the ECU.
Early log:
https://datazap.me/u/grant-runion/lo...zoom=2132-3518
Steps taken so far:
-Clean MAF
-Rescale MAF (100km driven on rescale flash)
-Return to a stock air intake (back on standard MAF scaled v4.03 tune)
-Replaced all 4 coils from a part out
-Injector cleaner (0km since putting it in)
Areas I can think of to try next:
-Clean throttle body
-Spark plugs (only checked one so far, looked fine)
-Clean injectors
-Try new MAF
-Try new O2 sensor (front I believe?)
Latest log:
https://datazap.me/u/grant-runion/40...d?log=0&data=1
Again, any insights or new direction is appreciated.