Negative Fuel Trims Under Load *Problem Solved*
 

I have extensively searched the forum and have found no replications of the issues I am having.

Vehicle: 2013 Subaru BRZ 50k miles
Mods:
* Jackson Racing Supercharger C38 Kit
* FFTEC Flex Fuel Kit
* Open Flash Tablet
* 2017 Intake Manifold
* Openflash Headers 2
* Invidia Overpipe
* Invidia catless resonated front pipe
* Invidia Q300 Cat-Back
* JRSC Engine Oil Cooler

Symptoms (Began <1 month ago):
* No CEL
* Loss of power
* Engine sounds raspy
* Fuel trims @ Idle range -2 to +2
* Fuel trims @ Cruise (no load) range -5 to +5
* Fuel trims under load range -6 to -16

Data logs can be found here:
http://www.datazap.me/u/njmaske/commute?log=0&data=1-12
http://www.datazap.me/u/njmaske/log-...=0&data=1-4-12
http://www.datazap.me/u/njmaske/log-...og=1&data=1-12

Potential Issues:

1) MAF Sensor
- 06/05 cleaned MAF Sensor with CNC MAF Cleaner (No Result)
- 06/05 replaced O-ring as precaution (No Result)
- 06/07 swapped MAF with a friend's (No Result)
2) 02 Sensor
- 06/05 Replaced due to original burning out
3) MAP Sensor
- Replaced not long ago due to failed omni 3 bar sensor. Readings appear to be accurate
4) Temperature
- IAT, Coolant, and Oil Temps are all within spec
5) Fueling Issue
- Direct injector seal - No popping signs or other indication
- Failing/Leaking/clogged Port Injector - Spark plugs are consistent with one another
6) Fouled spark plugs
- 06/07 - Replaced all 4, originals were consistent with one another
7) Vacuum Leak
- Manifold pressure floats around -9.85 -10.20 PSI @ Idle, I also checked to make sure my Evap hoses under the manifold were securely fastened with clamps
8) Boost Leak
- Logs indicate peak boost is 8.85 which appears to be a hair under what it should be. All inter-cooler piping is secured No other indications of boost leak.

***Update 06/05/2017 - During my drive home from work I experienced a severe loss of power. When I got home I plugged in my OFT and found my AFR reading 20 @ Idle with +35 fuel trims likely due to upstream 02 sensor failing.

***Update 06/05/2017 - I replaced the Primary 02 sensor with a new one which now accurately reads AFR, however, the initial issue remains. I assume the 02 sensor burnt out due to high exhaust temps from the engine leaning out.

***Update 06/07/2017 - I replaced all 4 spark plugs, applied heat tape to coil packs, changed oil and oil filter. This did not solve the issue. Old spark plugs looked good (light brown, not white nor wet)

***Update 06/07/2017 - I decided to unplug, clean, and reinstall most accessible plugs and hoses in the engine may. Towards the end I decided to test my JRSC check valve between my PCV Valve and Intake Manifold. I sucked on the manifold side of the valve, it would open as intended. I blew on the Manifold side of the valve and some air would get through. I suspected this could be the culprit since metered air could escape and pressurize my crank case. I replaced the JRSC valve with a Boomba Check valve and reinstalled everything. The fuel trims finally returned to normal.

***Updated 06/11/2017 - I removed the Boomba Check Valve and replaced the OEM PCV valve with a STI PCV Valve eliminating the need for an additional check Valve. WOT pulls look great and fuel trims are normal once again!!!!

PROBLEM SOLVED!!!

Your vacuum reading seems low, my turbo car idled at -19, -20. This would indicate a potential vacuum leak.

I believe you are reading vacuum in InHG. Mine is in PSI and -9.9 PSI is equal to 20.15 InHG.

Gotcha, units bit me in the a$$ :w00t:

Car been running completely fine since then?