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2000 Subaru Impreza 2.5rs Silv
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Discussion Starter · #1 ·
Well, I've had this problem for as long as I can remember, but for SOME reason I just haven't tended to it since my car has been through so much and i've just accepted it.

I have an sti shortblock with vf39, emanage ultimate, and other necessary turbo goodies. Running stock actuator spring PSI max, (7 or 8 lbs I believe).

Now, whenever I give more than half throttle, my car literally doesn't produce any power. You can just hear the exhaust shut off. I think its the spark plugs because whenever this happens, it sounds like there's no firing, but I can smell gas fumes pretty strongly. I find this strange though because I changed my spark plugs and it did this before that too. Not sure what spark plugs I have, but I know they're no NGK copper cores, I'm going to get some and see if that solves it

I can go through the power band smoothly if I don't stomp on it. It's really weird. Sometimes when i'm in the '1/2 throttle middle zone', may car jerks TREMENDOUSLY. My whole body jerks front and back wildly until I step off the gas. It's like the cars giving quick bursts of fuel, or maybe the spark plugs are firing randomly.

My car runs perfectly fine otherwise. I just find it annoying because I feel like I haven't ever found my car's true potential power.

Thanks guys!
 

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2000 Subaru Impreza 2.5rs Silv
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Discussion Starter · #3 ·
I got it done at Forged Performance so I would assume it was good. I really don't remember when this problem originated though, that's the problem.
 

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Green 97 OBS
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This sounds eerily similar to what my car did when the O2 crapped out and gave false rich readings. ECU pulled it's limit of fuel and car fell on its face, then at near WOT, it'd jump to open loop and dump fuel in again, giving that 'jerk'.
 

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00RS Coupe, 00RSwaggin
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I just replaced a faulty O2 in my car and it was causing the AFR's to be all over the place, and at idle would really struggle to hold and idle and run lean.

Almost does sound like fuel cut also, do you have any injector seals leaking on the intake? Maybe an injector leaking at high psi?
 

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'00 RS 205/221 '05 LGT 5EAT
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Bump for a solution. I have the exact same problem on my car. 1/3 throttle is fine, but if I go WOT the car just starts jerking. My AEM wideband shows the car is running lean off the scale when I'm on WOT and that jerking happens. Runs stoich under 1/3 throttle at 5lbs, I guess stock injectors can't handle boost or something. But there is a plethora of other problems with my car so I can't say for sure that it's a fueling issue, but that would be my guess.
 

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Shoelace Express (Walking)
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876 Posts
Funny. My bike is acting like this as well. I can't go past 4000rpm. After that there's no power. Subbing to this to get more answers :)
 

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2000 Subaru Impreza 2.5rs Silv
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1,436 Posts
Discussion Starter · #16 ·
I'm glad i'm not the only one! (Not to be a dick:p)

I am running 565cc injectors, so I don't think my issue is with the injectors not being able to keep up. How would I check a leak? Maybe a smoke test?

Changing the plugs today so i'll keep you updated. What do you guys suggest I gap them to?
 

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2000 Subaru Impreza 2.5rs Silv
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Discussion Starter · #17 ·
Well, changed the spark plugs and thought initially it was running smoother. (Changed them to NGK copper BKR7E's gapped at .038). But, of course, it was still the same.

I should also add that when I give throttle (less than 1/2 throttle) till I hit boost (above 0 psi on my boost gauge), then floor it it goes smoothly. It only happens when I initially floor it before hitting boost. Any advice/suggestions?
 

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Green 97 OBS
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You ought to data log a bit, especially if you have a way to watch the OBD-2 outputs. Can give you a better idea of what is causing it. If its sensor related, you'll see either the ignition advance being pulled (usually a knock sensor), fuel being pulled (Usually O2 sensor) or one of your sensors like the TPS, MAF, or MAP reading strange. Emanage can pull some of that IIRC, but I'm pretty sure the O2s aren't one of them.

A scan gauge is a good alternative if you don't want to go through the hassle of data logging, you can watch it in real time.

I still think its the O2 causing it, your problems are identical to mine with both a crapped out sensor and a universal sensor (never waste your money on those, go through the dealer). The short term fuel trims were a dead give-away. Was pegging at -30%, the ecu's limit to pull.
 
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