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Old 08-21-2019, 01:45 AM   #1
Ej20ForesterGuy
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Join Date: Jul 2019
Location: Canada
Vehicle:
02 Forester XT

Unhappy Surging Horsepower Under Hard Acceleration

Ok, so I've been having this issue since I got the car a month ago.

Car is a 2002 JDM Forester XT with EJ205 motor. In the last month I have changed the oil, air filter, spark plugs, coolant, serviced the rear dif, got an alignment, and I only run 94 octane in it. Yesterday, I pulled the MAF sensor out and cleaned it. It was really dirty and I'm already getting more power and mileage.

The issue is sometimes I feel like the car has 150 horsepower between 3000 and 4000rpm, then other times it feels like it has 220. It comes and goes. Sometimes while I'm driving, I'll have the throttle at a constant level, then the power will just kick in out of nowhere. Torque converter maybe?

I also occasionally hear a faint scratching sound coming from the front right of the car during hard acceleration. Like someone brushing a pop can with a wire brush. This is a little more often than the power changes, but as I said, only noticeable during hard acceleration. I also hear a moderately loud buzzing noise at idle, almost like a fan is hitting a piece of plastic. Not sure if all these symptoms are related. Just want to give as much info as possible.

Would really like to figure this out before something becomes seriously damaged if it's not already.

Thanks for the insight. You guys have been great so far.

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Last edited by Ej20ForesterGuy; 08-21-2019 at 02:17 AM.
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Old 08-21-2019, 09:42 AM   #2
motoryder
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Chapter/Region: SCIC
Location: The Mullet Mafia
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.... MLTMFA2
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Check for a loose knock sensor. Top of the block, has one wire going to it. The sensor has one bolt holding it down. If it rattles it will mimic the symptoms you describe.
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Old 08-21-2019, 11:56 AM   #3
subaru_gc8
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2004 WRX wagon
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I would be careful about the hard acceration. dependant on the noise it could be the wastegate opening to real knock. you have to remember that the jdm 205 had 9:1 compression so its going to be a little more prone to knock. if you have a way to data log that would be best. if you dont, put some e85 or buy a can of torco and put that in your tank to see if the sound goes away. if it does. than you know its real knock and I would suggest you go get a tune.
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Old 08-21-2019, 04:32 PM   #4
car_freak85
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Location: Cascadia
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EA63 , EA81T, EJ20G,
EJ205

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So you just removed and cleaned the MAF, eh? Did you disconnect the battery and press the brake pedal to clear the ECU's stored memory?

Check all vacuum lines and plastic unions for leaks/cracks/tears or breaks.
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Old 08-21-2019, 10:04 PM   #5
Ej20ForesterGuy
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I did not reset the ECU. I've driven the car probably 150km, so wouldn't the ECU relearn? Probably wouldn't hurt either way. Mechanic said the knock sensor had been replaced recently. I just bought the car like a month ago.
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Old 08-22-2019, 09:29 AM   #6
motoryder
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.... MLTMFA2
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Quote:
Originally Posted by Ej20ForesterGuy View Post
I did not reset the ECU. I've driven the car probably 150km, so wouldn't the ECU relearn? Probably wouldn't hurt either way. Mechanic said the knock sensor had been replaced recently. I just bought the car like a month ago.

Again, make sure that it isn't loose. I had the same issue on mine way back when where the car would feel gutless, pick up like it had full power and then fall on its face again right around the RPMs you described.

If it's securely tightened...well then I got nothin'.
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Old 08-22-2019, 10:56 PM   #7
Valarius Starchaser
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Hybrid 6MT Swapped WRB

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Metal brush like sound I would start with checking the turbo for shaft play and pre turbo connections for leaks
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Old 08-24-2019, 05:45 PM   #8
Ej20ForesterGuy
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Yep. Turbo is done. It's not even boosting anymore. Found this. It's a TD04L from a 2004 WRX, but I'm wondering if it would fit on my 2002 Forester XT

https://www.kijiji.ca/v-engines-and-...3JHkOTWcDejUez

Last edited by Ej20ForesterGuy; 08-24-2019 at 05:59 PM.
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