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Old 05-04-2010, 09:40 AM   #1
izzay
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Default '09 Impreza 2.5i Knocking

Now that the weather is good and the windows are down, I've noticed some mild knocking (or valve clatter?) on shifting. No throttle, clutch down, shift, and as soon as I'm letting off the clutch and going back on the gas I get a quick knock/clatter from the engine. I can't tell where the knocking is since I have to be driving.

I followed one other bit of advice, filling the car up with premium, and the knocking disappeared. To save money ($.50 between 87 and 93), I went down to a mix of 87 and 89 and it's still enough to keep the engine from knocking. I'm hoping I've identified the issue as the fuel, and not the fact that its 20°F warmer out than when I first noticed the knocking.

Any ideas? I've tried all brands of gas, Shell, BP, Citgo, and it doesn't seem to matter what I use-the knocking is still present.
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Old 05-15-2010, 11:37 PM   #2
sir_wagon
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Does it knock only once per shift, or does it knock or ping for a period of time?
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Old 05-17-2010, 09:14 AM   #3
Ogden
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Does it sound like a true knock, or more like valve train chatter?
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Old 05-18-2010, 03:20 PM   #4
izzay
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Quote:
Originally Posted by sir_wagon View Post
Does it knock only once per shift, or does it knock or ping for a period of time?
It knocks/pings once, very quickly, per shift.

Quote:
Originally Posted by Ogden View Post
Does it sound like a true knock, or more like valve train chatter?
It's hard for me to differentiate, as I can't hear it unless the window is open and I'm moving at a low enough speed that road noise is a minimum. At the same time, it sounds much louder than the valve train clatter/ticking on my old car, so I think its true knocking.

Last edited by izzay; 05-18-2010 at 03:26 PM.
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Old 05-26-2010, 03:06 AM   #5
roland678
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we have 2, and they both make the same kinda feathery metal grinding weird sound...id say its too quiet to be knocking tho.
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Old 05-30-2010, 11:43 PM   #6
imprezaowner
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that "knocking" happens whenever you shift incorrectly, happens to me when i go slow and mess up on my shift.
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Old 09-24-2010, 12:46 PM   #7
izzay
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This is now happening on the highway, and I've run premium gas to eliminate the bad/low-octane gas variable. At highway speeds, if I gently put pressure on the accelerator, I hear a loud clatter/knock for a second or two. I have NO CEL, and no codes on OBDII.

Took it in, dealer said the clunk was normal engine noise from a boxer engine and that I was shifting wrong. They 'taught' me to rev up the engine before a shift, and slip the clutch. I can smell burning clutch and am not happy with their explanation to cause damage to the car intentionally.

Two scenarios:

-Low rpm shifting: at 2000rpm, I almost let off the gas just as I get on the clutch, shift and blip the throttle as I let out on the clutch in a nonlinear fashion (fast at first, slow at the engagement point). Nice, perfectly smooth shift, and knocking.

-High rpm shifting: at 3000-3500rpm, I do the same as previously, but wait for the rpms to drop (the throttle seems to hold at high rpms for a second before dropping), then shift. Again, smooth and more knocking.

Add to that the dealer way. Shift between 2500-3000rpm. Rev the engine when I push the clutch in, and slip it until I engage the clutch in gear. Sorry, this is NOT the way AWD shifting should work. The explanation has been similar to turning up the radio to drone X noise in my car.

What's going on here, and shouldn't the car register a code?

Edit: I checked all the body pieces around the engine, exhaust heat shields, etc, and all is nice and tight, no metal on metal.
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Old 09-25-2010, 11:20 PM   #8
kuj5681
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I tought 2.5i is designed for regular fuel. It might be from the transmission?
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Old 09-26-2010, 01:25 PM   #9
Ogden
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To me, this sounds like the usual valve-train chatter that is typical of these engines. Sounds bad, but my previous 2.2 liter did it, and it was still running at 350k. My 09 does it too, always associated with shifting. You can slip the clutch a but and make it stop, but I never really bothered.
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Old 06-20-2020, 06:13 PM   #10
ellorno
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how did this turn out? i'm looking for a similar, but different, tick/knock sound diagnosis
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Old 07-08-2020, 12:09 PM   #11
Emoss704
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Is this post dead?
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Old 07-17-2020, 05:42 PM   #12
vsi1600
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I'm pretty sure I have engine knock on an 08 2.5i OB with 100k miles.

It only does it under load when you are holding the gas down. Higher gears are more likely to cause it, but the issue has nothing to do with shifting.

I have been running mid-grade in Denver, but will switch to 91 the next time I am at the car to see what it does.

It definitely sounds like pre-ignition pinging (hopefully not detonation as well.) I suspect carbon buildup could be the cause but I don't have a boroscope to check that..

Will post back after I change gas grades.
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