Welcome to the North American Subaru Impreza Owners Club Sunday November 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 > Engine Management & Tuning

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 08-20-2004, 01:01 AM   #1
CrashTestRacer
Scooby Newbie
 
Member#: 66394
Join Date: Jul 2004
Location: Rochester, NY
Vehicle:
2004 WRX Wagon

Default Coming off accelerator can be scary

I have a 2004 WRX Wagon. I have a very noticable problem that I've seen discussed on these forums before. When the engine is pulling hard and you can feel that incremental increase in torque. It's a great feeling...up until I begin to come off the throttle - If the clutch isn't already down - the engine will surge to no throttle and then back to "mostly throttled but where you actually came down to" in a matter of a second. The car actually bucks. I've had it to varying degrees from major "that might of hurt the driveline" to annoying and unsmooth.

I think that this is a controller problem and that ther might be a software fix. Does anyone have any thoughts on this? Any suggestions for the cheapest way to fix it and stay mostly stock? Is there something I'm missing and could it be a hardare problem?
* Registered users of the site do not see these ads.
CrashTestRacer is offline   Reply With Quote
Old 08-21-2004, 10:04 AM   #2
splurta
Scooby Newbie
 
Member#: 42072
Join Date: Aug 2003
Chapter/Region: NESIC
Location: Cambridge, MA
Default

If I am understanding you correctly, I thought this was an issue with the stock engine (and perhaps also transmission mounts) being soft.
splurta is offline   Reply With Quote
Old 08-21-2004, 01:26 PM   #3
carguyx
Scooby Newbie
 
Member#: 66850
Join Date: Jul 2004
Location: TURBOTRIX
Vehicle:
04 green'd STI
11.41 @ 117mph 93 oct.

Default

Sounds like compressor surge to me if I am reading it right.

VERY BAD FOR YOUR MOTOR!!!!!

You have a BOV on the car? I bet its not opening correctly.
carguyx is offline   Reply With Quote
Old 08-21-2004, 02:35 PM   #4
el~sharko
Scooby Specialist
 
Member#: 29735
Join Date: Nov 2002
Chapter/Region: MAIC
Location: Westminster,MD
Vehicle:
2011 JSW TDI - DSG
2008 EVO X MR

Default

Quote:
Originally Posted by carguyx
Sounds like compressor surge to me if I am reading it right.

VERY BAD FOR YOUR MOTOR!!!!!

You have a BOV on the car? I bet its not opening correctly.
why is it bad for the motor?
el~sharko is offline   Reply With Quote
Old 08-21-2004, 03:45 PM   #5
hippy
Scooby Specialist
 
Member#: 36528
Join Date: May 2003
Location: florida
Vehicle:
2002 Impreza Wrx
Silver

Default

Sounds like you need to push the clutch in earlier or let your foot off the gas later.
hippy is offline   Reply With Quote
Old 08-21-2004, 03:49 PM   #6
Macabre
Scooby Specialist
 
Member#: 3841
Join Date: Jan 2001
Location: Sacramento, CA
Vehicle:
2004 WRX Wagon
UTEC+VF22+WI

Default

This is a very common '04 problem. Aftermarket engine management is one possible fix. Gone since UTEC'd, here. Some people seem to have had some success getting the dealer to fix it somehow, but it sounds like you've probably read that in the old threads on the subject.
Macabre is offline   Reply With Quote
Old 08-21-2004, 03:55 PM   #7
carguyx
Scooby Newbie
 
Member#: 66850
Join Date: Jul 2004
Location: TURBOTRIX
Vehicle:
04 green'd STI
11.41 @ 117mph 93 oct.

Default

Your turbo is blowing forced air into the motor, then the throttle plate slams shut, but the turbo is still pushing tons of air into the closed throttle plate. A BOV working the right way would dump that air out of the valve. What happens if it doesnt though is it creates a turbulence of air that blows back into the turbo and can spin the turbo back wards or make the wheel break apart, or it can force the throttle plate open and put tons of unmetered air into the chambers. LEAN AS HELL. If this is happening get your car checked out ASAP.

What mods are you running?
carguyx is offline   Reply With Quote
Old 08-21-2004, 05:34 PM   #8
Macabre
Scooby Specialist
 
Member#: 3841
Join Date: Jan 2001
Location: Sacramento, CA
Vehicle:
2004 WRX Wagon
UTEC+VF22+WI

Default

Err.. force open the throttle plate? Even if that did happen, which is extraordinarily unlikely, the air would still have been metered. If you're positive that it's gear lash, soft bushings, a bad bypass valve, driver error, etc, read this thread to make sure your theory isn't already debunked: http://forums.nasioc.com/forums/showthread.php?t=502483
Macabre is offline   Reply With Quote
Old 08-21-2004, 05:43 PM   #9
carguyx
Scooby Newbie
 
Member#: 66850
Join Date: Jul 2004
Location: TURBOTRIX
Vehicle:
04 green'd STI
11.41 @ 117mph 93 oct.

Default

Im not saying thats whats happening, it does happen is extreme cases though. There was a video of a supra a few months back on here that it was happening to.
carguyx is offline   Reply With Quote
Old 08-21-2004, 07:22 PM   #10
blackie
Scooby Specialist
 
Member#: 42979
Join Date: Sep 2003
Location: houston tx
Vehicle:
03 wrx
blizzzack stage IV

Default

sounds to me like you should press the clutch in next time you get into boost and then let off the gas. learn to drive the awd suby allittle better, because all the extra moving parts on our drivtrain as compared to a front drive car arent as forgiving when you decide to motor break after you hit boost.
blackie is offline   Reply With Quote
Old 08-22-2004, 02:10 PM   #11
02WRX2.5
Scooby Specialist
 
Member#: 63192
Join Date: Jun 2004
Chapter/Region: NWIC
Location: Portland, Or
Vehicle:
02 wrx
157mph trap

Default

i have an 02 wrx and it never did it untill EM, I have also had been on the dyno and had great tunes to where I didn,t have this at all. S I think it's in the factory EcU and can be tuned out. Unfortunatly my current tune does have this trailer hitch feel. Time to get back on the dyno.
02WRX2.5 is offline   Reply With Quote
Old 08-23-2004, 12:55 PM   #12
maestro
Scooby Specialist
 
Member#: 53021
Join Date: Jan 2004
Chapter/Region: SCIC
Location: West Hollywood
Vehicle:
'04 Forester - sold
'72 Datsun 240Z

Default

"Sounds like compressor surge to me if I am reading it right.

VERY BAD FOR YOUR MOTOR!!!!!

You have a BOV on the car? I bet its not opening correctly."

I agree... Sounds very similar to something I've experienced before: Once on my turbo'd SE-R I didn't have the bypass valve hooked up correctly and it wasn't opening at all. When I let off the throttle after boosting, the car would lurch and stumble violently; it didn't make for smooth driving at all. It would even happen just trying to modulate the throttle. Once I rerouted the hoses, problem solved. There was audible chattering though as the air bounced back and forth in the intake pipe... If the air bounces back and stalls the compressor blades, that's also stalling the turbine blades, obstructing the exhaust flow, hence the stumbling. I don't think it's pushing the throttle plate open.
maestro is offline   Reply With Quote
Old 08-23-2004, 01:49 PM   #13
mrbigisbudgood
Scooby Specialist
 
Member#: 54378
Join Date: Feb 2004
Chapter/Region: South East
Location: Charlotte, NC
Vehicle:
2013 Mazdaspeed 3
Black

Default

My '04 does this on the factory software. Cobb 93OCT Stage 2 made the bucking issue less dramatic, but didn't solve the problem.
mrbigisbudgood is offline   Reply With Quote
Old 08-23-2004, 05:08 PM   #14
CrashTestRacer
Scooby Newbie
 
Member#: 66394
Join Date: Jul 2004
Location: Rochester, NY
Vehicle:
2004 WRX Wagon

Default

Last I knew this thread was almost off the page...Thanks for all the feedback. The car is stock, so it has stock boost control, off course. Also, this happenes AS I come off the throttle, as in the first impulse of my foot off WOT. High in the RPM range, and more noticable when the engine is being expecially "incremental".

I appreciate all the input concerning mounts, drivetrain play, or driver snafu. But it is clearly not that. In my very best attempts to ease off the throttle the engine will f-up and release and then re-engage in a way thet feels FAR worse than I could ever mimick using drivetrain play and engine throttle.

That is the thread I was refering to, Macabre. What has been defunked?

Interesting the concept of boost lash-back, but since I'm purposly trying to ease off the throttle rather than cut off, it's not the same set up. The car only does this at times (though reliably).

My thoughts are on a ECU program glitch, but maybe it could be hardware. UTEC seems to get around the problem.
CrashTestRacer is offline   Reply With Quote
Old 08-23-2004, 05:53 PM   #15
Macabre
Scooby Specialist
 
Member#: 3841
Join Date: Jan 2001
Location: Sacramento, CA
Vehicle:
2004 WRX Wagon
UTEC+VF22+WI

Default

CTR: In that thread, there was one individual (ImportVenom) who reported that the dealer was able to fix the problem with some new parts. Since you're still stock and want to remain that way, I think your best bet is to try and reproduce it for a dealer tech.
Macabre is offline   Reply With Quote
Old 08-24-2004, 08:35 PM   #16
MISTSHIFT
Scooby Newbie
 
Member#: 54544
Join Date: Feb 2004
Location: San Diego
Vehicle:
2003 WRX SEDAN
WRB

Default

I have an 04 that used to do the same thing when it was stock. I think I have read just about every post on cobb and here about it. There doesnt seem to be any conclusive information on the problem. I personally went to the stage 2 just to get around that problem, and that does work. According to what I have read, I think a few thing happen that produce the effect. When the ECU switches from open to closed loop in the 04 there is a brief period when the engine stumbles and that is amplified through the soft tranny and engine mounts in the WRX. I went to Cusco motor and tranny mounts to get rid of the symptoms but that probably just puts more shock on the already questionable geas in the tranny. You can try a wastegate adjustment, that seems to help the feel of the car all around. In my mind Im still trying to figure out exactly how that would effect it, but it does. I did 1 turn shorter on the arm, and that seemed to take a lot of the jitters away including the bucking, I think that the factory doesnt always get the tension right on the assembly line. The new COBB stage 1 map works really good for the 04 its really smooth. I eventually went full stage 2 and thats the way the car should have been released in the first place, it doesnt even matter what gas you use, it always runs awsome. The factory tune just isnt that great, I think maybe they had to detune the car to get it into the US Just my observations
MISTSHIFT is offline   Reply With Quote
Old 09-16-2004, 04:44 PM   #17
CrashTestRacer
Scooby Newbie
 
Member#: 66394
Join Date: Jul 2004
Location: Rochester, NY
Vehicle:
2004 WRX Wagon

Default

I'd like to bring this thread back to the top to see if anyone else has any ideas, found the problem, or found any dealer that has heard (and admitted) to the problem. It's very annoying to have a herky jerky car every time I try to ease off the accelerator under hard acceleration.
CrashTestRacer is offline   Reply With Quote
Old 06-11-2005, 12:27 PM   #18
Davemeister
Scooby Specialist
 
Member#: 86577
Join Date: May 2005
Location: D1cKSh0Tz [ON] OFF
Vehicle:
2015 Supercoolmobile
Awesome Pearl Metallic

Default

Hey CrashTestRacer... my car could not be any more stock. It is an '05 with 1500 miles on it. Mine did it too, the first time I went WOT in 3rd gear. But the 2nd time it happend, it seemed less severe. Have you reset your ECU lately? Seems like I read that the ECU will "learn" around this and minimize the effect. That does seem to be what is happening with my car. I did it again yesterday and I hardly felt anything at all.
Davemeister is offline   Reply With Quote
Old 06-11-2005, 01:41 PM   #19
x99percent
Scooby Specialist
 
Member#: 27108
Join Date: Oct 2002
Chapter/Region: MWSOC
Location: Detroit-ish, MI
Vehicle:
2004 STi
2004 A4

Default

Quote:
Originally Posted by carguyx
...it can force the throttle plate open and put tons of unmetered air into the chambers. LEAN AS HELL.
I can guarantee that, unless you've got a leak, any air that makes it to the motor has been metered.
x99percent is offline   Reply With Quote
Old 06-11-2005, 10:51 PM   #20
Equilibrium Tuning
NASIOC Vendor
 
Member#: 26933
Join Date: Oct 2002
Chapter/Region: BAIC
Location: Fairfield, CA
Vehicle:
2006 STI
CGM

Default

I've seen this happen on several cars. Its an issue with the stock ECU. If any of you have logging software, try to log the issue. You'll most likely see a severe lean spike as you transition out of WOT at high RPM's. I'm not sure what the root of the issue is as the stock fuel map has fairly appropriate values in that region. It can certainly be tuned around, but it seems that there may be something mechanical at the root of the problem.
FYI: both cars I've seen this on have stock BPV's and both were cured by tuning.

Thanks
-- Ed
Equilibrium Tuning is offline   Reply With Quote
Old 06-12-2005, 01:07 AM   #21
hippy
Scooby Specialist
 
Member#: 36528
Join Date: May 2003
Location: florida
Vehicle:
2002 Impreza Wrx
Silver

Default

It has nothing to do with tuning. There's a thread somewhere on nasioc(I'm not gonna search) that talks about puting a restrictor inside the tube which is connecting to the turbo inlet pipe and comes from the pcv valve. They say that helps with the bucking, and also helps the rpms drop quicker. I too have a bucking type of sensation sometimes when I'm laying off the throttle, even just while cruising around, but I think the rpms drop fine on my car when I shift right

peace
hippy is offline   Reply With Quote
Old 06-12-2005, 01:26 AM   #22
WRXRgr
Scooby Specialist
 
Member#: 54942
Join Date: Feb 2004
Chapter/Region: South East
Vehicle:
2004 WRX

Default

I'm still skeptical on this issue. While it's attributed to MY04s, I've seen threads where 02 and 03 drivers jumped in and said they had it, too...the only common factor was that it only happens on manual transmissions, never on auto trannies.
WRXRgr is offline   Reply With Quote
Old 06-12-2005, 12:58 PM   #23
JRSCCivic98
Scooby Specialist
 
Member#: 67080
Join Date: Jul 2004
Default

OK people, this is most definatly an OEM ecu tune problem. Get yourself some GOOD engine management like EcuTek from a respectable tuner and be done with it. I had these same issues on my car. Also, the people that have APs and state that the problem is still there... it's an AP map problem. It took Cobb months to fix the stalling issue with 04's because they thought they could take the easy way out and run 05 code on them. It took them even longer to finally resolve the CL/OL delay issues that were still evident in last years AP maps (some debate that the issue is still not resolved the best way it can). Their maps just aren't the best in the world, but then again for all you lovers out there, that's my opinion from what I have seen with my own 2 eyes.
JRSCCivic98 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
W.H.O. Finally Comes To The Realization That Traffic Can Be Deadly AVANTI R5 Non-Subaru News & Rumors 0 06-17-2009 08:27 AM
can stock turbo inlet come off in one piece without removing the manifold? jcbluescooby Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 23 04-09-2009 07:08 AM
Should I be at all mad that this is slowly coming off? nxttruck2002 Interior & Exterior Modification 7 06-15-2008 02:23 PM
Any USDM cars come with HIDs that can be swapped into H4 headlights? BrysImpreza Electrical & Lighting 0 11-28-2003 12:37 PM
Beware who you cut off... A sad commentary on how petty people can be. ttoversteer New England Impreza Club Forum -- NESIC 14 01-10-2002 12:30 PM


All times are GMT -4. The time now is 04:13 PM.


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.