Erratic AFRs at light boost or idle?

MS3_Rez

MS3_Rez

Greenie N00B Member
Looking for help diagnosing a weird issue with wandering AFR under light throttle. There is not an obvious vacuum leak causing this had already done boost leak test to 25psi. Started Happening after changing downpipe, catback and BOV.

Year/Make/Model: 2010 Speed 3
Mileage: Body:148,000 Engine:~68,000

Concern: AFRs are not hitting the target under light load, throttle, most commonly happens under cruising condition after just letting off (BOV Releasing pressure). Idle also seems to have issue settling at 14.7 at random times as well. AFR seems to get thrown off every time I let off when in boost usually varying between 13.xx - 15.xx. The amount of time for it to settle back to 14.7 seems to be getting longer every time I drive it. LTFT is generally around -6 cursing and 0 when giving some throttle. Occasionally throws multiple misfire code p0300 but goes away within the next couple times of starting the car.

DTC's: None related, one code for VTCS delete, one code for EGR delete and O2 sensor for catless pipes.

Modifications: TR8 FMIC, Mazdaspeed 3 Turbo Downpipe Exhaust SS Racing Stainless Steel Generic, Mazdaspeed3 Gen2 (10-14) Catback Exhaust, Stock manifold VTCS delete, HKS SSQV BPV, XspeedFab Injector seals, Damond EGR full Delete, Corksport 3 inch Power Series Intake, CST4, Corksport ECBS, Autotech HPFP internals, NGK 6510 spark plugs, Corksport OCC.

ECU/Tuning Software: Cobb Accessport

Tuner: Will (At PD Tunning)

Diag already performed: Boost and vacuum leaks searched for and eliminated with pressure and smoke tests. Wastegate vacuum lines and ECBS valve were checked. (Plan to replace primary o2)
 
Are you actually using a blow off valve as in releasing air back to the atmosphere after is has been through the MAF? If that's the case then it is what it is. If you want solid AFR s you have to run in recirculating
 
Easter Bunny said:
Are you actually using a blow off valve as in releasing air back to the atmosphere after is has been through the MAF? If that's the case then it is what it is. If you want solid AFR s you have to run in recirculating
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I understand this but when i give it more boost around like 15-17psi and let off it tends to get stuck around 13.38-13.58 for a solid 15 or so seconds. When stopping on a light tends it sometimes will sit at 13.38 for like 5-10 seconds before jumping to15.xx then quickly settling at 14.7. I understand that my AFR will be different with a full vta BOV but is what I'm experiencing normal? I will be uploading logs here and sending them to my tuner later today.
 
If you are venting to atmosphere your afrs are going to be all fucked up for a few seconds after you close the throttle. You should be running recirc.
 
Easter Bunny said:
If you are venting to atmosphere your afrs are going to be all fucked up for a few seconds after you close the throttle. You should be running recirc.
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Sorry i get that they will be fucked for a few seconds but here is my data log i was able to get on the way home. Best example of what is going on. But in this case it literally got stuck at 13.xx almost the whole log. Someone mentioned could be a sticky primary o2. I will be swapping it this weekend.
 

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What BOV are you using? Fuel trims don't look terrible, you could try swapping primary O2 sensors if you have a spare. You may have damaged it when swapping the DP.
 
DISIFTW said:
What BOV are you using? Fuel trims don't look terrible, you could try swapping primary O2 sensors if you have a spare. You may have damaged it when swapping the DP.
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I’m using HKS SSQV now. Ya I was thinking that I possibly damaged it when replacing DP. I didn’t see any visual damages tho. I will be swapping it tomorrow morning to see if that is what it possibly is
 
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