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.
Hesitation/Studer @ 3k-4k RPM
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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.
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.
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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Did you get to the bottom of the issue. I have a similar issue on a 2019 WRX with Invidia h/flow cat jpipe, R400 catback , BigSF intake, GFB BPV. Issue only started after installing BigSF from stage 1 (stage 1+BigSF map) Runs fine after an ECU reset for a few weeks then slightly rough idle creeps in for a day with some interesting exhaust popping/afterfire then next day big hesitation on WOT/boost and exhaust popping/afterfire. Reset the ECU again and it’s fine. Done this four times now. Cobb have reviewed the diagnostics file and can’t see an issue but have queried the GFB BPV which they haven’t tested in their setup. I’ve ensured the installation is correct for the BigSF (pod filter 1 inch from lip of pipe), cleaned MAF and MAP, replaced plugs, performed smoke leak test. May send to Cobb again for another look.
Ordered another MAF sensor just in case and if no change will reinstall the stock intake and ECU reset to test. Can always go protune if needed but this Cobb stage 2+BigSF OTS should work just fine.
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