Welcome to the North American Subaru Impreza Owners Club Tuesday September 23, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Factory 2.0L Turbo Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 04-07-2013, 08:16 PM   #1
PlasticFoamMan
Scooby Specialist
 
Member#: 197764
Join Date: Dec 2008
Chapter/Region: NESIC
Location: Broston
Vehicle:
02 WRX Stage DD
PRND 01G

Default Strange noise under part throttle & vacuum

Perhaps someone else has run into this issue before I start tearing things out from under the hood to find the problem.

Over the past couple days, I've developed (or noticed) a strange rattle under part throttle and vaccum at about neg 10 lbs, primarily with the motor under load. If I hold vacuum here, the noise sounds sort of similar to an electronic gauge stepper motor cycling, only louder. I can cause this to happen in any gear and only when holding vacuum as noted above--if I'm actively going into boost, it only makes the noise for a moment, which is how I first noticed it.

No boost issues or leaks, motor pulls strong and sounds great otherwise. I assume my waste gate doesn't have any issues as I still hear the usual flutter as normal (thin dp). I tried bringing revs up in my parking garage and the noise is not audible at all with the hood open or outside the car, but with the windows closed and with the motor not under load it is only briefly notable when in the cabin. This made me think it could perhaps have something to do with my mechanical boost gauge (the sound is very much "in the cabin" or almost "on the dash" or so it would seem).

I'll try to shoot a video later, but I'm not sure I have any audio equip nice enough to pick up the sound. Has anyone ever heard something like this? Possibly the turbo? Mech gauge going bad?

I am completely since mechanically everything feels and otherwise sounds absolutely fine.

Thanks for any input!


Edit: and just to note a couple other bits, oil pressure, egt's, temps, all normal. Last maintenance was Rotella synthetic over the weekend...
* Registered users of the site do not see these ads.

Last edited by PlasticFoamMan; 04-07-2013 at 08:22 PM.
PlasticFoamMan is offline   Reply With Quote
Old 04-07-2013, 09:10 PM   #2
Uncle Scotty
Scooby Guru
 
Member#: 16200
Join Date: Mar 2002
Vehicle:
OK Houston
we have an Uncle

Default

is the trans dipstick pushed in all the way???

Uncle Scotty is offline   Reply With Quote
Old 04-07-2013, 09:17 PM   #3
PlasticFoamMan
Scooby Specialist
 
Member#: 197764
Join Date: Dec 2008
Chapter/Region: NESIC
Location: Broston
Vehicle:
02 WRX Stage DD
PRND 01G

Default

Hah, yup, everything is secure. I figured it was something stupid at first but nothing I can find that's obvious. I went over the damn engine bay for a solid 30 trying to find something but came up empty handed

Its only ever under vacuum at the exact same point so I figure it must be something mechanical somewhere, I've just never heard a noise like it before.
PlasticFoamMan is offline   Reply With Quote
Old 04-07-2013, 10:23 PM   #4
Uncle Scotty
Scooby Guru
 
Member#: 16200
Join Date: Mar 2002
Vehicle:
OK Houston
we have an Uncle

Default

well..shizzle.....unbolt the boost solenoid and let it just hang free...use a zip tie to make sure it doesnt get bounced around too much

see if that is it
Uncle Scotty is offline   Reply With Quote
Old 04-08-2013, 05:42 AM   #5
sevier2
Scooby Newbie
 
Member#: 295516
Join Date: Sep 2011
Chapter/Region: SCIC
Location: San Diego area
Vehicle:
2004 WRX
Silver

Default

I had a weird knocking sound coming from my car every day in 2nd gear for about a year. I FINALLY found it about a week ago. Turns out the down pipe had been rubbing up against the crossmember. Look for parts that may be touching other parts of the car that it's not supposed to...
sevier2 is offline   Reply With Quote
Old 04-08-2013, 01:15 PM   #6
PlasticFoamMan
Scooby Specialist
 
Member#: 197764
Join Date: Dec 2008
Chapter/Region: NESIC
Location: Broston
Vehicle:
02 WRX Stage DD
PRND 01G

Default

^^ I'm guessing it may be something rubbing and is simply exhaust resonance related. It seems at second glance this may actually be happening at around 2k rpm in any gear when the engine is under load.

I broke the exhaust bolt that mounts the dp to the trans a long time ago and that bracket makes a really irritating noise all the time when driving (I'm very lazy and haven't fixed this for some reason). That distinctly sounds like its coming from under the car, however. This sound is more in the cabin or on the dash... as soon as I have time I'll keep testing this out.
PlasticFoamMan is offline   Reply With Quote
Old 04-09-2013, 08:11 PM   #7
PlasticFoamMan
Scooby Specialist
 
Member#: 197764
Join Date: Dec 2008
Chapter/Region: NESIC
Location: Broston
Vehicle:
02 WRX Stage DD
PRND 01G

Default

This proved to be pretty difficult sound to capture, mainly because of its volume and also that it is momentary, but here is a video. You can distinctly hear it come on at 4-5 seconds in and again at 28 seconds (and 2-3 seconds if you are listening carefully). It is very hard to replicate.

http://s79.photobucket.com/user/stev...0_594.mp4.html

This sound is audible in the video but do not mistake it for the loud tires, turbo, or my frustration with other drivers.

Any thoughts? Doesn't sound bearing or valve related to me. I've never heard it before.
PlasticFoamMan is offline   Reply With Quote
Old 04-16-2013, 12:51 PM   #8
PlasticFoamMan
Scooby Specialist
 
Member#: 197764
Join Date: Dec 2008
Chapter/Region: NESIC
Location: Broston
Vehicle:
02 WRX Stage DD
PRND 01G

Default

And to close the loop on this, now that I've had a second to not be the one driving, the sound is actually coming from the rear of the car

Now I'm at a complete loss
PlasticFoamMan is offline   Reply With Quote
Old 08-15-2014, 10:24 AM   #9
misfitsfreak81
Scooby Newbie
 
Member#: 346751
Join Date: Feb 2013
Default

Ever figure this out? I've got a similar issue and this is the only thread I've seen that comes close to it? My noise is a light rattle noise heard in all gears only under ~10 inches of vac and at 3100-3300 rpm. If below or above those areas car sounds normal.

I've checked all the vac and boost leak problem areas and everything seems good. I do have a thin wall equal length header on the car if that makes any difference. Other than that just your basic stage 2/2+


Sent from my iPad using NASIOC
misfitsfreak81 is offline   Reply With Quote
Old 08-31-2014, 09:02 PM   #10
PlasticFoamMan
Scooby Specialist
 
Member#: 197764
Join Date: Dec 2008
Chapter/Region: NESIC
Location: Broston
Vehicle:
02 WRX Stage DD
PRND 01G

Default

It turned out to be stereo wire plugs in the trunk left by the previous owner

It seems they were sitting in just the right location and way such that exhaust resonance/drivetrain vibrations caused them to rattle against the firewall. Very strange, but by process of elimination this was the source (for your issue, check for loose or partly loose things in the trunk!)
PlasticFoamMan is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 01:23 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.