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Old 07-10-2019, 08:30 PM   #1
Aallgire
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Exclamation Lean and breaking up in boost?

Hey guys I've been lerking here for awhile and finally have a reason to post. So to start with I bought a built car, ran fantastic when I get it and for months after.
But now, when you take off from a stop with the AC on its absolutely gutless and barely moves. Once it gets moving it's okay. You can't really get past 50% throttle becuase it shoots to lean and breaks up and cuts out. Normal daily driving it just feels kinda gutless. No strange noises smoke or anything.
It has alot of mods. I'm hoping to get soemthing more than "take it to the tuner" and bullying about buying a built car and not doing it myself, as that is all some Facebook groups can seem to provide.
Edit: it's gutless with AC off, but not as bad. With AC on it almost stalls, off it's driveable just kinda pathetic
Side note at idle on the AP it's reading -9.5 psi, from reading I thought that should be alot lower. Like -14psi

Vigilant street plus short block
Wiseco Pistons
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Torque solutions TMIC
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DW 265lph fuel pump
Grimmspeed boost control solenoid
IA performance Fpr
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Tsudo catless downpipe, straight pipe
Steamspeed xts 20g turbo
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Last edited by Aallgire; 07-10-2019 at 08:31 PM. Reason: To clear confusion
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Old 07-10-2019, 09:51 PM   #2
alexmartynyuk
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Is it tuned in maf or speed density? If on maf still then check for leaks between the maf sensor and the turbo itself. A 20g setup may be a little laggier than stock but not to the point you are describing. Do you have a wideband? How are you verifying it swings lean under load?
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Old 07-10-2019, 10:29 PM   #3
Aallgire
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Quote:
Originally Posted by alexmartynyuk View Post
Is it tuned in maf or speed density? If on maf still then check for leaks between the maf sensor and the turbo itself. A 20g setup may be a little laggier than stock but not to the point you are describing. Do you have a wideband? How are you verifying it swings lean under load?
Thank you for the reply!
It's tuned on maf still, I've never felt the car stock ive only known it since it's had the 20g. It does have a wideband, but I also have been checking the AF ratio on the accessport just to make sure the wideband isn't reading wrong, but when it cuts out it's extremely noticeable, wideband jumps to 16+ then the car kinda bucks and sputters. And as you accelerate harder, the leaner it runs.
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Old 07-10-2019, 10:44 PM   #4
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At this point I would definitely not drive it in boost and check for a torn turbo inlet or maybe the after maf hose. And also you may actually be blowing out spark which will register lean but actually isn’t. I would pull your plugs out and check them out and make sure all the connectors on the coil packs are latched because that is a common failure point.
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Old 07-10-2019, 10:53 PM   #5
Aallgire
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Quote:
Originally Posted by alexmartynyuk View Post
At this point I would definitely not drive it in boost and check for a torn turbo inlet or maybe the after maf hose. And also you may actually be blowing out spark which will register lean but actually isnít. I would pull your plugs out and check them out and make sure all the connectors on the coil packs are latched because that is a common failure point.
Oh trust I don't touch boost lol. If I do it's maybe 3 or 4 psi getting on the highway, I read about spark blow out which lead me to replace the plugs twice and make triple sure they're gapped right. I'll check the coil packs tho, I looked up how to make a smoker to test for that inlet leaking I'll try that tomorrow. So both of you are thinking more than likely a major boost leak?
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Old 07-10-2019, 11:15 PM   #6
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i believe they mean pre turbo. also check and make sure nothing is getting in the maf as in dirt or debris, check for a tear in the air filter or inlet, the clamps, bypass return tube. So usually if it's a boost leak (after turbo) it would run more rich under more load. Also what is idle afr? Af learning value?
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Old 07-10-2019, 11:23 PM   #7
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Originally Posted by PWpaperweight View Post
i believe they mean pre turbo. also check and make sure nothing is getting in the maf as in dirt or debris, check for a tear in the air filter or inlet, the clamps, bypass return tube. So usually if it's a boost leak (after turbo) it would run more rich under more load. Also what is idle afr? Af learning value?
Idle afr is usually 14.2-14.6, I'm not sure off the top of the head the learning value. I didn't think about the bypass return, I have 0 clue where it even goes so that very well could be it.
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Old 07-10-2019, 11:49 PM   #8
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I know I'm new here, so forgive me if these are dumb questions.

Does it idle alright or do the RPMs jump around?

If the car is sitting at idle and you do a quick stab on the throttle, do the RPMs drop really low and then come back up when it tries to return to idle?
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Old 07-10-2019, 11:53 PM   #9
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Both of who lol, I was the only one who was replying to this thread. But no I don’t think it’s a boost leak, if you had a boost leak then it would be doing the opposite and going extremely rich. I think you have either spark blowout or a leak between the mass airflow sensor and the cold side of the turbo. There is so many spots that it could be pulling air. You can also somewhat verify this by looking at logs, one of the symptoms would be low g/rev even at boost.
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Old 07-11-2019, 12:00 AM   #10
Aallgire
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Quote:
Originally Posted by scriptkiddy View Post
I know I'm new here, so forgive me if these are dumb questions.

Does it idle alright or do the RPMs jump around?

If the car is sitting at idle and you do a quick stab on the throttle, do the RPMs drop really low and then come back up when it tries to return to idle?
It usually idles good, sometimes does kinda vary up and down then settle. And yes if you blip the throttle it sometimes goes way low like it wants to stall, but never does then comes back
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Old 07-11-2019, 12:01 AM   #11
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Quote:
Originally Posted by alexmartynyuk View Post
Both of who lol, I was the only one who was replying to this thread. But no I donít think itís a boost leak, if you had a boost leak then it would be doing the opposite and going extremely rich. I think you have either spark blowout or a leak between the mass airflow sensor and the cold side of the turbo. There is so many spots that it could be pulling air. You can also somewhat verify this by looking at logs, one of the symptoms would be low g/rev even at boost.
1 guy replied once prior lol sorry, I'll look for g/rev on the AP and log it. Just drive normal then or get into boost?
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Old 07-11-2019, 12:21 AM   #12
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Well I would say if you had a log then it would be nice to look it over but don’t intentionally take it into boost. Just look things over really well, see if you can introduce smoke into the system to check for obvious leaks and go from there.
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Old 07-11-2019, 12:22 AM   #13
Aallgire
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Quote:
Originally Posted by alexmartynyuk View Post
Both of who lol, I was the only one who was replying to this thread. But no I donít think itís a boost leak, if you had a boost leak then it would be doing the opposite and going extremely rich. I think you have either spark blowout or a leak between the mass airflow sensor and the cold side of the turbo. There is so many spots that it could be pulling air. You can also somewhat verify this by looking at logs, one of the symptoms would be low g/rev even at boost.
Cruising down the road going 60 calculated load g/rev is .85-.70
Af learning 1 is -10.16
Inj duty cycle is 5.5ish
Boost is -4.8 to -5.8psi
Maf g/s is 27-31
All live numbers as I'm driving it now
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Old 07-11-2019, 12:22 AM   #14
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What turbo inlet does the car have by the way?
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Old 07-11-2019, 12:22 AM   #15
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Quote:
Originally Posted by alexmartynyuk View Post
What turbo inlet does the car have by the way?
Stock turbo inlet
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Old 07-11-2019, 12:25 AM   #16
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Originally Posted by Aallgire View Post
Stock turbo inlet
It is fairly common for them to tear right where the clamp is for the turbo. It may not look obvious but I have seen it happen a lot.
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Old 07-11-2019, 12:26 AM   #17
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Quote:
It usually idles good, sometimes does kinda vary up and down then settle. And yes if you blip the throttle it sometimes goes way low like it wants to stall, but never does then comes back
Those are usually signs of a vacuum leak. Usually a vacuum leak won't cause all of the power loss you're experiencing unless it's really bad (in my experience).

I know that the turbo inlet hoses on the WRX tend to get mushy and develop leaks over time(happened to mine). So, I second what the other people in this thread are saying about a pre-turbo leak.

Additionally, if the car has a cheap aftermarket turbo inlet, those have been known to collapse/deform under high vacuum, especially with bigger turbos. That said, it would be strange to have the inlet pipe be fine for months and then all of sudden start collapsing.

If it were my car, I would check the following:
1. Turbo inlet pipe
2. other pre turbo pipes
3. Vacuum lines

Oh, and this one may be a long shot, but check your fuel filter. It could be clogged and causing your lean condition.
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Old 07-11-2019, 12:27 AM   #18
Aallgire
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Quote:
Originally Posted by scriptkiddy View Post
Those are usually signs of a vacuum leak. Usually a vacuum leak won't cause all of the power loss you're experiencing unless it's really bad (in my experience).

I know that the turbo inlet hoses on the WRX tend to get mushy and develop leaks over time(happened to mine). So, I second what the other people in this thread are saying about a pre-turbo leak.

Additionally, if the car has a cheap aftermarket turbo inlet, those have been known to collapse/deform under high vacuum, especially with bigger turbos. That said, it would be strange to have the inlet pipe be fine for months and then all of sudden start collapsing.

If it were my car, I would check the following:
1. Turbo inlet pipe
2. other pre turbo pipes
3. Vacuum lines

Oh, and this one may be a long shot, but check your fuel filter. It could be clogged and causing your lean condition.
Where on Earth is the fuel filter? Isnt it an in tank?
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Old 07-11-2019, 12:32 AM   #19
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Quote:
Where on Earth is the fuel filter? Isnt it an in tank?
On my GD, it's under the hood on the driver's side near the strut tower.

Didn't notice the OP had a newer WRX. Looks like it's in the tank on an 08.
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Old 07-11-2019, 12:32 AM   #20
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Quote:
Originally Posted by alexmartynyuk View Post
It is fairly common for them to tear right where the clamp is for the turbo. It may not look obvious but I have seen it happen a lot.
I'm gonna do a smoke test tomorrow, I made this little smoke canister with a soldering iron. Is it safe to just put that right into the intake hose? Or do I need to cap stuff off? Won't be much pressure at all
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Old 07-11-2019, 12:35 AM   #21
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Quote:
Originally Posted by Aallgire View Post
I'm gonna do a smoke test tomorrow, I made this little smoke canister with a soldering iron. Is it safe to just put that right into the intake hose? Or do I need to cap stuff off? Won't be much pressure at all
No need to cap anything off itís not gonna harm anything. Just donít set it on fire lol, and good luck!
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Old 07-11-2019, 02:43 PM   #22
PWpaperweight
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Also before going through all that have you taken a look at your maf. Like maybe a piece of debris is in it or it's really dirty. It's only 2 screws to pull it out. Just might be the easiest thing to start off with is all, before trying to hook up your smoke tester. Also what is af learn, and af Correction at idle it can tell us a lot. A dirty or debris filled maf with make it run rich at idle and as airflow increases it will go lean. Everything Alex had said though is good advice
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Old 07-11-2019, 04:44 PM   #23
Aallgire
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No need to cap anything off itís not gonna harm anything. Just donít set it on fire lol, and good luck!
So I did the smoke test and all the lines to the boost controller were leaking at barely any pressure. Tightened that up, then the intercooler piping on the back at the Y pipe had a rubber hose that was to far forward and on a notch making it leak. So fixed all that, made sure the maf was clean. My boost gauge reads way different than the accessport tho. The gauge will read 10psi but the car would read almost 20 on the AP. I tried one time to push the throttle hard and it just completely fell on its face. The inlet didn't have a lick of smoke during the test, so what's next? The coil pack having a loose or bad connection?
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Old 07-11-2019, 04:47 PM   #24
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Quote:
Originally Posted by PWpaperweight View Post
Also before going through all that have you taken a look at your maf. Like maybe a piece of debris is in it or it's really dirty. It's only 2 screws to pull it out. Just might be the easiest thing to start off with is all, before trying to hook up your smoke tester. Also what is af learn, and af Correction at idle it can tell us a lot. A dirty or debris filled maf with make it run rich at idle and as airflow increases it will go lean. Everything Alex had said though is good advice
I've replaced the maf once thinking that was the culprit, but to make sure I cleaned it again and still the same result
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Old 07-11-2019, 04:59 PM   #25
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Quote:
Originally Posted by Aallgire View Post
I've replaced the maf once thinking that was the culprit, but to make sure I cleaned it again and still the same result
I had that problem too, turns out the stock afr o2 sensor was bad. just a fyi make sure you use oem subaru for any metering sensors ie maf and o2, also have you noticed your gas milage falling off a bit?
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