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Discussion Starter · #1 ·
After months of researching and troubleshooting this issue on my own, I feel like I've run out of options, so maybe someone here can point me in the right direction. I will try to be as detailed as I possibly can, but it's always difficult to adequately explain issues like this to someone who can't physically see what's going on with the car. I will include a full list of every modification already done to the car in regards to the engine and drivetrain, as well as a list of what has already been replaced to try and rectify this issue and maintenance that needed to be performed anyway. If I left anything out, feel free to ask.

Car: 2006 WRX
Mileage: 87k
Mods:
VF39
STI TMIC
Tomei turbo inlet
AEM cold-air intake
Cobb 3-port EBCS
Tomei equal length exhaust manifold
Grimmspeed EWG uppipe
Tial MV-S 38mm EWG
Invidia catless downpipe
TGV deletes
AEM 320 fuel pump
Perrin air-oil separator
Fluidampr crank pulley
Group N motor mounts
Perrin transmission mount
Perrin pitch stop mount

Currently tuned to 19 PSI by Eric Minehart at Torqued Performance

Replaced:
All timing belt pulleys, tensioner, belt, and water pump
All rear engine seals
Engine wiring harness
MAF sensor
Injector o-rings
Intake manifold and TGV gaskets
Intercooler y-pipe and BPV gaskets

I had a smoke test performed and my mechanic and I were able to confirm that there are no vacuum leaks. All grounding wires are good and snug. There are no counts of cylinder roughness during the knock events, AFRs are normal, no issue hitting target boost, and DAM stays at 1. No exhaust leaks. No CELs. Oil changes have always been done no later thank 3500 miles and only with high quality oil.

Now, onto the issue. For the past few months, I have been experiencing excessive feedback knock, with values ranging from your normal -1.4 to -2.8, as high (low?) as -11.8. These knock events only occur immediately following shifting from 2nd to 3rd gear, at approximately 25-40% throttle, and between 2200-2500 RPMs. Never above 3000 RPMs. If I shift slowly and roll onto the throttle, no knock event occurs. I've discussed this at length with my tuner and he says it is most likely false knock, but of course it still worries me. Additionally, I have been experiencing cold start issues, but I am unsure if they are related. In cold weather (>40 degrees), there is a knocking sound coming from the engine bay, but it never lasts for more than 30-45 seconds at the absolute most. I've seen quite a few people say that this noise can be attributed to piston slap, which from what I understand can be a common occurrence on older Subaru motors. My car is 12 years old, so that seems to logically follow. Apart from that, however, the car will sometimes sputter and almost stall on start-up, with choppy idle for about 60-90 seconds before it stabilizes. I have also noticed that even with the TGVs deleted, the car still runs lean on cold starts, about 16.5:1. And most recently, my car will occasionally experience a delay of about 1 to 2 seconds between turning the key in the ignition and actually turning over. There are no sounds whenever this occurs, just silence and no response. I replaced the starter in the event that perhaps the solenoid on my old one was going out, but it has still happened a couple of times since then. Once the car gets up to operating temperature, none of these issues persist except for the feedback knock

Thank you for reading. Any insight would be greatly appreciated.



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Discussion Starter · #3 ·
I will allow someone more knowledgeable to answer on most of these issues. Supplying a datalog will help tremendously with us assisting you as to what the issue may be.

But I will add this, the knock sensor on these cars is famous for picking up false knock (loose heat shield rattling, a/c compressor kicking on and off, etc). But I had a similar issue with my Torqued Performance map on my last wrx. ***Now before I speak any further, I am not bashing Eric or TP in any way as many people are tuned by him and have had satisfying results.***

But, when I had my TP tune on my 11 wrx I was experiencing very similar issues with the feedback knock. It was literally all over the place. I ran the map for about a year and never had any real issues with the car other than the feedback knock issue. Eric at the time also wrote this off as false knock (which it may have very well been). But about a year after using his maps with a few different changes from Eric, I added some new parts and took the car to IAG for a protune. After the protune the feedback issues were gone.
You know, you're not the first person I've heard about who had issues with a TP map. Eric has been my tuner for about a year and a half now, and he's been great (quick turnaround time, answers questions really fast), but I'll admit I have found myself wondering if this is a tune issue. I'll see if I can find the last set of logs I did for this current map and post them here. If I can't find them then I'll do some tonight and have them posted tomorrow.

Edit: I've gone over everything in the engine bay (multiple times) even remotely close to the knock sensor that could be causing vibrational feedback but found that nothing was loose.

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Discussion Starter · #4 ·

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Discussion Starter · #8 ·
If you are reading a knock of -11.8 you would hear it with your own ears. Radio off, do you actually hear the motor ping at all? If not, it is most likely a false knock of some sort.
Nope, I've never actually heard any audible knock whenever the knock events occur. It's probably a little bit of false knock and a little bit of my motor is getting tired. Either way, I'm getting a motor build this summer.

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