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Hesitation/Studer @ 3k-4k RPM

1411 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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How many miles are on the car it self? Have you ever had the carbon cleaned off the valves yet? The way these things self tune/learn this stuff can be hard to lock down some times. Are you getting a DAM drop at all? Any Knock or knock learning? Do you always buy your fuel from the same place?

If you have a DAM drop get fuel from a different station and add 1 gallon of E85 to it if you can get it. See if that helps. If it does then you know it’s as simple as fuel quality issue. I used to buy fuel from a local place and all the sudden about 6 months ago I was having odd issues. Started keeping my Accessport in the car and saw DAM drops. I switched stations and it all went back to normal. I don’t know what they but they changed something when they went to a “Top Tier Fuel” verified station.

You can also reload your tune. A lot people say don’t do this. Some say do it. See if the self learning has gone a little out of Wack.
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check your dam. Knock that low with no dam isn’t a big deal. You will loose your Ecu learning but try to just reflash your tune.
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