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Old 01-10-2018, 12:43 PM   #1
BoxerLove
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Default Wont rev past 4500-5000 RPM Under load

Ok scratching my head here. Figured I would reach out for some outside input.

Recently Dropped a brand new OEM shortblock in my 2005 STI

Mods:

Catless up and DP

Rebuilt Big 16G

Walbro 255

Stock BCS

Big TMIC

Silicone inlet

Injen Intake

Carberry SD map

Brand new upstream o2

New VSS

------------------------------

When in neutral you can rev the car to redline no problems. This issue only happens under load in every gear. Ive tried 3 different sets of coil packs and replaced and checked the gap on brand new OEM NGK Iridium plugs. Set gap to OEM Spec. No change in the way it ran. Ive checked around for boost leaks and even went as far as replacing my TMIC Y pipe gaskets.


Not totally sure whats going on. Car misfires/wont rev past 4500-5k under load in boost. Running on 10PSI now and just started getting into boost as ive been just driving carefully during break in. The car does have an ABS light on for what I believe is a sensor, Just haven't got it in to have the code scanned yet. Brand new VSS as I was having an issue with my speedo but it ended up being the "BACK" Fuse blown on the interior fuse panel.

Ive done a fuel pressure test at the rail after the dampeners and had plenty of fuel pressure (60+LBS.) I pulled the intake and replaced the Fuel Pressure Regulator vac lines just to eliminate that being an issue.

The only thing I havent checked is the TGV's. The car does still have them. Could they be causing an issue like this? I read somewhere that Carberry and TGV's dont get along well. So ive been thinking about deleting them. Although I dont have any codes what so ever, not even a misfire code.


Any and all input is greatly appreciated. Been pulling my hair out with this one lately.
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Last edited by BoxerLove; 01-10-2018 at 01:43 PM.
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Old 01-10-2018, 01:14 PM   #2
viper_crazy
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Curious, do you have flat foot shifting or launch control limits set in your accessport (assuming you have one)? If so, your foot may be activating the switch that's at the top of the clutch, signaling to the ECU to hit that rev limiter that's set for FFS/LC.

Only reason why I ask, is because that exact thing happened to me.
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Old 01-10-2018, 01:17 PM   #3
BoxerLove
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Quote:
Originally Posted by viper_crazy View Post
Curious, do you have flat foot shifting or launch control limits set in your accessport (assuming you have one)? If so, your foot may be activating the switch that's at the top of the clutch, signaling to the ECU to hit that rev limiter that's set for FFS/LC.

Only reason why I ask, is because that exact thing happened to me.
No AP here, Just an open source Carberry Speed Density tune. Cant finish the tune until I figure this issue out. Mapped for 10PSI until I do. Car boost fine and pulls good until 4500-5k and then falls right on its face. Almost like the power band just hits a wall and wont rev past that point. You can feel the car missing/running like crap. But only under load at/between those RPM Levels
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Old 01-10-2018, 01:21 PM   #4
viper_crazy
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Ah, I'm out of ideas. What you were describing sounded very similar, is all.
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Old 01-10-2018, 01:22 PM   #5
BoxerLove
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Quote:
Originally Posted by viper_crazy View Post
Ah, I'm out of ideas. What you were describing sounded very similar, is all.
No problem, Appreciate the input. Ive been a bit stumped.
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Old 01-10-2018, 01:57 PM   #6
rtv900
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Quote:
Originally Posted by BoxerLove View Post
No AP here, Just an open source Carberry Speed Density tune. Cant finish the tune until I figure this issue out. Mapped for 10PSI until I do. Car boost fine and pulls good until 4500-5k and then falls right on its face. Almost like the power band just hits a wall and wont rev past that point. You can feel the car missing/running like crap. But only under load at/between those RPM Levels
but it can't be the powerband hits a wall if it's in every gear.
It'd be one thing if in 6th at 120mph you can't pass 5k, but you said every gear?
So even in 1st or 2nd?
There's so much torque in those gears there's hardly any load at all, so it has to be an ECU issue just cutting out the throttle.
What viper said makes sense, although maybe it isn't launch control specifically, but some sort of control just over riding you.

do you have a way to view ACTUAL throttle position?
I'd bet your throttle is backing off right at 4500 regardless of your foot.
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Old 01-10-2018, 02:20 PM   #7
BoxerLove
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Quote:
Originally Posted by rtv900 View Post
but it can't be the powerband hits a wall if it's in every gear.
It'd be one thing if in 6th at 120mph you can't pass 5k, but you said every gear?
So even in 1st or 2nd?
There's so much torque in those gears there's hardly any load at all, so it has to be an ECU issue just cutting out the throttle.
What viper said makes sense, although maybe it isn't launch control specifically, but some sort of control just over riding you.

do you have a way to view ACTUAL throttle position?
I'd bet your throttle is backing off right at 4500 regardless of your foot.
I'll hookup my tactrix and check again. But yes every gear as soon as you enter boost at those rpm's
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Old 01-10-2018, 03:01 PM   #8
Subie_
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Have you checked out the cylinder roughness data parameter? I know it's not the most competent gauge, but it might help narrow things down a bit if it's not kicking a CEL. A pending engine code may exist as well.

The upstream O2 sensor is new, but it doesn't come into play during open loop fueling under boost. What's your IDC and AFR in the problematic range? I assume your simply running your previous tune, with the exact same hardware (just new block)... no new mods/ additions?

Calculated load = (60*MAF voltage)/ RPM... perhaps your MAF sensor is on the fritz and craps the bed when you reach a certain load.

You can pull the ABS code using FreeSSM software and a VAG-COM 409.1 cable; yes, a VAG-COM cable. Google is your friend.
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Old 01-10-2018, 03:10 PM   #9
BoxerLove
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Quote:
Originally Posted by Subie_ View Post
Have you checked out the cylinder roughness data parameter? I know it's not the most competent gauge, but it might help narrow things down a bit if it's not kicking a CEL. A pending engine code may exist as well.

The upstream O2 sensor is new, but it doesn't come into play during open loop fueling under boost. What's your IDC and AFR in the problematic range? I assume your simply running your previous tune, with the exact same hardware (just new block)... no new mods/ additions?

Calculated load = (60*MAF voltage)/ RPM... perhaps your MAF sensor is on the fritz and craps the bed when you reach a certain load.

You can pull the ABS code using FreeSSM software and a VAG-COM 409.1 cable; yes, a VAG-COM cable. Google is your friend.
I'll do a log and post the results. I'm on a speed density base map from my tuner so the maf isn't being used. Just for IAT. I do have freessm and a vagcom cable as well. From what I understood only the dealer could read the codes on the 05. But I'll hook it up and see what I can read.

I bought the car blown up with 9k miles on the setup. Kid threw a 20g on and no tune. Go figure lol. Heads were gone through by a professional Subaru shop in traverse city Michigan. I checked them over before my build and everything visually checked out. I went with a big 16g instead of the 20g.

Last edited by BoxerLove; 01-25-2018 at 07:42 AM.
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Old 01-13-2018, 07:17 PM   #10
JSR84
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Sounds like the same issue I had with an 05 Ford Focus I owned. Car idled and drove fine until you put some load on it in the upper RPM's where it would just stop accelerating kind of felt like a soft rev limiter. Turned out to be a dying fuel pump. The idle and cruzing fuel pressure was within spec but the second you put load on it the fuel pressure would fall right off.
When I pulled the pump the sock was full of debris, I likely could have cleaned the sock and left the factory fuel pump but ended up replacing it as it was starved several times and I had the tank dropped anyways.
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Old 01-25-2018, 07:42 AM   #11
BoxerLove
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Quote:
Originally Posted by JSR84 View Post
Sounds like the same issue I had with an 05 Ford Focus I owned. Car idled and drove fine until you put some load on it in the upper RPM's where it would just stop accelerating kind of felt like a soft rev limiter. Turned out to be a dying fuel pump. The idle and cruzing fuel pressure was within spec but the second you put load on it the fuel pressure would fall right off.
When I pulled the pump the sock was full of debris, I likely could have cleaned the sock and left the factory fuel pump but ended up replacing it as it was starved several times and I had the tank dropped anyways.
I drove the car with an electronic in line fuel pressure gauge installed at the hose on the rail and pressure was good. 60+ PSI. Finally getting back around to diagnosing this being my 98 LGT decided to **** the head gaskets (35k on the current set.) Been rough in the subi scene for me lately.
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Old 01-25-2018, 07:42 PM   #12
BoxerLove
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Had some time to do some more diag tonight. Pulled the intake manifold off and manually opened the TGV's, put the motors back on and left them unplugged to eliminate them from ever being closed. Tuned out the codes etc, Car still ran the same. Darn.


Also had a buddy running romraider logger as I drove, and under 7.25 PSI @11.14 AFR at 100% throttle the car builds to anywhere in the 4500-5k range then goes lean (like 16 17 AFR) and Cuts fuel. Quite odd. Im really tempted to eliminate the in take fuel filter (temp to eliminate the possibility of it clogged) , and possibly even replace the 255 pump with a stock known good STI pump as I truly dont need the 255 at my current setup. Any opinions here? IDC's were only hitting 69% max. So that answers the earlier question of if the ECU is seeing the correct throttle or pedal %.

Driving at a normal speed and normal daily driving all values are completely normal. 14.7 afr while at highway speeds under light throttle etc. So odd. I was truly banking on a stuck TGV or something along those lines.
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Old 01-25-2018, 07:46 PM   #13
BoxerLove
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Worst case I do have a spare ECU around, But I would have to make an appointment with the dealer to have the immobilizer flashed. Which Im sure isnt cheap. Ill have to call.
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Old 02-02-2018, 02:32 PM   #14
Silversedan3G
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Sounds like a tgv cel in limp mode. Probably need a pro tune?
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Old 02-04-2018, 09:32 PM   #15
STIpls
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I had this issue in my 05 Wrx while running carberry. I had disabled the tgv’s the way you mentioned but under boost it would force them closed and choke out!
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Old 02-07-2018, 07:51 AM   #16
BoxerLove
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Originally Posted by STIpls View Post
I had this issue in my 05 Wrx while running carberry. I had disabled the tgv’s the way you mentioned but under boost it would force them closed and choke out!
Mine are unplugged and manually put to the open position. Thought i had it figured out for sure. Starting to go through the fuel system here soon. Replacing the in tank filter, all the rubber lines and potentially the regulator under the IM. The car did sit for 3-4 years before I got it. The issue went away for awhile and now is back just as it was if not a tad worse. Ive smelt fuel on cold startup and shortly after starting to drive the car. This has been a big ole PITA.
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Old 02-07-2018, 08:13 AM   #17
BoxerLove
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Also recently got a P0172 (sys too rich bank 1) code and a CYL1 missfire code. Just adding for documentation. Possible intermittent sticky injector? Will update with findings. LTFT is out of whack and ill get the log and post. On a buddys laptop.

Last edited by BoxerLove; 02-07-2018 at 08:24 AM.
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Old 02-07-2018, 08:18 AM   #18
viper_crazy
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Just curious, how are your TGV flaps held open?
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Old 02-07-2018, 10:06 AM   #19
BoxerLove
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Originally Posted by viper_crazy View Post
Just curious, how are your TGV flaps held open?

Manually opened, Motors put back on and left unplugged so they can not move. A more permanent TGV delete is to come. We were just trying to see if this was the definite cause or not.
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Old 02-07-2018, 10:16 AM   #20
viper_crazy
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Quote:
Originally Posted by BoxerLove View Post
Manually opened, Motors put back on and left unplugged so they can not move. A more permanent TGV delete is to come. We were just trying to see if this was the definite cause or not.
The flaps can't be forced closed under WOT?

I've never heard of this done before, is why I'm asking.
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Old 02-07-2018, 10:21 AM   #21
BoxerLove
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The flaps can't be forced closed under WOT?

I've never heard of this done before, is why I'm asking.
A friend of mine said hes done (and helped me with the process as I didnt understand what he ment talking over the phone) this many times with no issues. Now you have me wondering. Might just go ahead with a proper delete when I replace the rubber fuel lines under the intake that I should have done last time it was off. Eliminate the issue of a TGV restriction totally.
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Old 02-07-2018, 07:37 PM   #22
STIpls
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Default Wont rev past 4500-5000 RPM Under load

That’s what I was saying. I did the same thing as you and one side was still able to be forced closed. Drove me absolutely nuts
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Old 02-07-2018, 07:50 PM   #23
viper_crazy
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If you're able to hook the TGV position sensor portion back up without the motor control and read it, it may be easier to see if they have or not.

Idk how that works. Maybe I'm talking out me arse.

Last edited by viper_crazy; 02-07-2018 at 08:43 PM.
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