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EJ Subaru Rich Condition on Idle - A/F Learning Negative

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Have some heavy negative readings on the AF learning on the idle area, (Ecu is pulling back fuel for some reason?)

Idle is rough, car drives fine other then a shitty idle.

Full list of mods to the car (MY09 Subaru Forester XT)

Brand new Shortblock from Subaru EJ257

Reconditioned Heads

VF52 Turbo

3 Port BCS Grimmspeed

3 inch Turbo back exhaust

TGV Delete

Air Pump Delete

PSR Silicone Turbo Inlet

Throttle Body Coolant Bypass

Dual Catch Cans

ARP Head Studs

FelPro Permaseal MLS head gasket

Standard Fuel Injectors/Fuel System/Pump

Attached Files

First thing I would do is pressurize the system with an air compressor to check for vacuum/boost leaks.


I have searched everywhere for vacuum leaks/boost leaks and yet to find anything. Admittedly I have not used a proper boost leak tester - but I don't think its the issue considering its running rich not lean?

The car ran fine prior on same tune before hand. It did not have the TGV and airpump removed along with the 3 inch turbo inlet pipe. But I doubted these would effect idle quality?

Pressurize the system before you do anything. Even if it doesn't solve this issue, it will prevent you from wasting your time tuning something that isn't running right. You'd be surprised the strange places where boost can leak out.

Did the same thing as that article, couldn't find any leaks.

Sounds like you need to scale the mass airflow sensor next. It's good that you have stock injectors installed, that eliminates injector settings as a possible problem.

The idle doesn't seem 100%, I don't think scaling the maf will fix it though.

Try scaling first. There's only so many things it can be. You have stock cams and electronic throttle. There is no check engine light right? The fuel trims will eventually cause one.

What is the current MAF scaling? Is it stock scaling? What if you put the full stock intake back on?

Its the stock airbox with a turbo inlet.

Here is the latest learning view from about a 45 minute drive. I reset the ecu before hand so the values were all 0 prior the drive.


My MAF sensor scaling is not stock, its +5% across the board from stock.

Ok. Put the stock air inlet back in, flash it with the stock scaling so you have 0 learning, and go do the same drive cycle. See what the trims look like in learning view.

Does this model have the BAP sensor still in the EGR solenoid? Have you removed that and just turned the code off?

Hey Rob,

I assume your talking about the sensor in the Airpump stuff? I cut it out of the sensor and plugged it back in. I can see the atmospheric pressure readings in romraider.

I put my normal 19psi boost tune on - the car built boost no problem so I don't think there is any vac leaks and didn't hesitate/do anything werid upon starting to build some boost. Only kept it at 50% throttle though.

I think just the MAF needs to be scaled due to the above mods.

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