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Old 01-20-2023, 12:31 PM   #1
Scooby Newbie
Member#: 532901
Join Date: Jan 2023
Question 2013 WRX AF Learning 1 at +25% at idle

Background Information
Within the past week, I noticed my car's power would drop noticeably once I hit around 5,6k RPM, typically in third gear pulls. There are no check engine lights.

Next, I noticed the AF Learning 1 value was at +25% while at idle. It seemed to always stay at this value. So this tells me the car's A/F ratio is running rich.

I removed and cleaned the MAF and MAP sensors. I did originally clean the MAF with isopropyl, so it might be busted now, but did buy the MAF cleaner and used that. I reset the ECU, ran the car, and AF Learning 1 starts at 0 then slowly creeps up to 25%.

I replaced the upstream A/F ratio sensor and the downstream O2 sensor. The downstream O2 sensor was black with carbon. The upstream one did not look terrible, but was a bitch to remove. Using OEM Denso parts for both.

Throughout this, the ECU was reset via the Accessport several times.

Current Issue
With these changes performed, the car seems to idle okay and has come up to operating temperature. I drove it around the block and it did not seem to like that. I'd come to a stop and it felt as if it would stall and throttle response seems delayed a second or so. Next, I turned it on again, and now it idles pretty rough.

I logged idle data for ~36 seconds this morning: https://docs.google.com/spreadsheets...it?usp=sharing
Another log, mostly at idle, but also moved the car forward and back: https://docs.google.com/spreadsheets...it?usp=sharing

This is my first post. I tried following the advice in similar posts, but feel a bit stuck. I'm not sure if there's a good resource for troubleshooting the fuel systems for 2013 WRX EJ25 motors. I've found loose information on the matter and have been piecing things together.

Last edited by muertos; 01-20-2023 at 12:44 PM.
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