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Old 11-16-2016, 07:50 PM   #1
Scooby Newbie
Member#: 171697
Join Date: Feb 2008
Chapter/Region: MWSOC
Location: Orland Park, IL
05 WRX 16G XT

Default Idle/Neutral 13 to 16 AFRs fluctuations


I have been having a fluctuating idle and when going into neutral gear for quite some time now, might have been ongoing for couple of years as I was never able to find the culprit, car never stalls luckily. The issue I'm experiencing is that the AFR are fluctuating between 13.0 to high 16s, issue is very apparent during warmup enrichment. Sometimes though the idle does manage to stay 14.7 stoich for a brief period. OL is fine, I do not have any problems in open loop nor when cruising with light pressure on the gas pedal (I can cruise at stable 14.3-14.9AFRs with light throttle but car will eventually accelerates and goes too fast). My tune is targeting 11 AFRs in OL. Car drives great and boosts quick, but idle drops lower than usual when shifting to neutral.

Can somebody please help me and take a look at the log? (log includes Innovate Wideband readings)

Mods are as follows
- '05 WRX, stock 2.0L EJ20, stock ECU, my own opensource tune (based off XPT Stage 2), I'm running 93 oct. 105k miles.
- APS 65mm CAI, the MAF has been scaled to best of my ability back when I ran stock 420cc injectors.
- 800cc decapped modded stock injectors (the scalar has been adjusted to hit 11AFRs and latencies/tip-in have been borrowed from one of the threads here on RomRaider)
- Blouch 16G XT turbo, Catless UP/DP, STi catback
- Hallman MBC, STi TMIC, stock BPV, TGV deletes, Walbro 255

Things that I have done up to this point.
- vacuum leak checks (tried to check many times to verify that my TGV deletes went ok, (1) first boost leak test I've done was from the throttle body, I successfully pressured intake manifold up to 10psi, (2) second boost leak test I tried to do was from the inlet, however my dip stick spew oil so I stopped--not sure why that happened, I followed multiple guides)
- loss of compression (e.g. cracked piston rings, bent/sticky valves)...compression tested fine, ~150psi in all cylinders.
- cleaned MAF many times (MAF voltage at idle seems to be stable at ~1.3v, I don't think MAF is bad)
- cleaned CAI filter many times
- checked for pre o2 exhaust leaks
- cleaned and inspected IACV many times
- cleaned crank/cam sensor 5k mi ago when
- did timing belt change myself 5k ago (also verified that timing is set properly and not off by 1 or anything)
- clogged injector or fuel pump (unlikely as have Walro 255 with clean sock-filter, although that was 50k mi ago, and I went from 420cc injectors to 550 to 800s, the AFR problem in idle/neutral has always been there, and got a bit more prominent as I went to bigger injectors)
- tried unplugging front o2 to force car into OL, didn't help much, problem still persists

Things I haven't or can't check
- unstable fuel pressure, bad fpr
- bad/accidental setting in ECU (possible human error while tuning)
- bad MAP sensor
- bad front o2 sensor (really thinking of getting new sensor soon though, might be my last resort, however I doubt my o2 is bad, it reads pretty close to my calibrated wideband)
- inlet duck could have a slit?

Things that I tried in my map
- raised idle to 850rpm
- raised idle timing by couple degrees in hopes of smoothing it out

Coldstart Log
The log has been logged for 8 minutes in 55F weather, cold start, right after ECU reset.

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