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Hesitation/Studer @ 3k-4k RPM

1412 Views 5 Replies 3 Participants Last post by  1KRX1
I drive a 2016 WRX 2.0L MT with Invidia turbo back catted exhaust and Cobb cold air intake on the Cobb stage 2+bigSF tune running 91 oct. fuel the best I can get in Utah. I've been running this tune for 20k miles and do oil changes every 3K miles. Last week I left my house to drive to work and I noticed when giving the vehicle around 40%~ or more throttle at 3k-4k RPM the vehicle will hesitate throughout that RPM range and after 4k-4.2k RPM the vehicle drives normally pulling full boost and is putting the power down as normal. What I've noticed while watching my boost and AFR at 100% throttle, the boost will be relatively normal but the AFR will go from 10.80 - 14.10, when normally while at 100% throttle the AFR is 10.14 - 10.90. I'm not sure what is going on but I have ordered a new air filter but it has not arrived yet, the spark plugs are NGK laser Iridium and only have 15K miles on them, I have never changed the coil packs while I've owned the vehicle but from what I can tell it doesn't seem like a spark issue. I'm more leaning towards fuel or air flow issue. If you need more info tell me what you need and I'll answer to the best of my ability! Thanks in advance.
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The vehicle has 97K miles on it. I have not done a valve cleaning on it myself I have thought about doing that. I have not been monitoring DAM but I will start monitoring it. I have switched gas stations while it’s been doing this and it’s continuing to do it. I have gotten -1.41 feedback knock on the accessport on occasion maybe once every 5-10 drives. I have thought about flashing the tune back to the stock tune and back to the tune that’s on it.
I checked my DAM it was at .825 when I started monitoring it, I reflashed my tune and it started driving normally again and the DAM went back up too 1.000. but while driving home today after fueling up at chevron with 91 the DAM dropped again to .6xx (I can't remember the last two numbers) but it wasn't hesitating like it was before, the power seemed to be down during a pull when I first noticed it but it felt pretty normal again after I did a second pull. I'm looking at a datalog I took when it was initially acting up before the reflash and at 3200-4100 rpm at 100% I was getting -6.33 fine knock learn but 0 feedback knock, is that bad? I'm going to take another datalog tomorrow and see if its doing the same thing. I'm also not the best at reading these datalogs I've never looked at them before.
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