Welcome to the North American Subaru Impreza Owners Club Sunday September 21, 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 > Normally Aspirated 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 02-08-2009, 12:58 AM   #1
DenT
Scooby Newbie
 
Member#: 201779
Join Date: Feb 2009
Location: Tri State
Vehicle:
2003 Impreza TS

Default Throttle release choppyness

No matter how lightly you release the throttle when in gear you get a small bounce/buck like you would if you let a clutch out too quick...It happense right at throttle release (full release). The situation would be if you release the petal and engine braking was occurring... There is not a smooth transition. It is magnified in the lower gears which is quite annoying as 1st second and 3rd around town bounces whenever your letting go of the pedal.

feels like slop in the gears but i doubt that's it. I know its not supposed to be like that because neither my bike or my civic do that. There is a smooth transition between accelerating and decelerating.

On another note (i'm not sure if its related) i get fault P0519
Idle Air Control performance

I cleaned out the IAC actuator and it still moves as i left it out and put the car in the on position. Perhaps i will take out the whole TB and clean it out later.


Well let me know your thoughts.
going to check for slop in the cables tomorrow.
* Registered users of the site do not see these ads.
DenT is offline   Reply With Quote
Old 02-08-2009, 01:22 AM   #2
RaceFaceXC
NASIOC Supporter
 
Member#: 165749
Join Date: Dec 2007
Chapter/Region: South East
Location: stupid Florida
Vehicle:
2007 No YELLING
on the bus!

Default

On my DBW vehicle i get this to the extreme. I modified the DBW throttle angle map to help it out a bit, but the real fix is stiffer engine and trans mounts according to anyone who has changed theirs. I have yet to change mine.
RaceFaceXC is offline   Reply With Quote
Old 02-08-2009, 02:11 AM   #3
Jerry Xu
Scooby Specialist
 
Member#: 36629
Join Date: May 2003
Location: Baltimore Maryland
Vehicle:
07 2.5i
Regularly Being Modified

Default

Mine does the same thing. i use neutral at low speed or gears 4 and 5 most times. 1 and 2 are particularly bad. It is good to know this can be resolved by stiffer motor/tranny mounts. I haven't studied, are you sure of this fix?
Jerry Xu is offline   Reply With Quote
Old 02-08-2009, 07:31 AM   #4
nojokesniper
Scooby Newbie
 
Member#: 192623
Join Date: Oct 2008
Location: NJ
Default

ur iac is causing it, when you let off the gas pedal, the throttle body closes, then the iac is supposed to open to let air bypass the throttle body so the car does not stall, but if your iac is not moving as well or as fast as it could your car is essentially almost stalling right when you let off the gas but then your iac slowly opens and allows it to run like it should

i would try to clean the IACs passage, maybe you have crud in there, if not maybe its time for a new iac
nojokesniper is offline   Reply With Quote
Old 02-08-2009, 10:44 AM   #5
DenT
Scooby Newbie
 
Member#: 201779
Join Date: Feb 2009
Location: Tri State
Vehicle:
2003 Impreza TS

Default

Well i cleaned out the IAC unit itself pretty well with some CRC electrical contact cleaner. Bunch of fine crud came out. I think i will do it again when it is at full extention. It is "functioning" as i had it out and put the ignition on to witness it move. As for its timing i dont really know hot to measure that. I'll give cleaning all the passages a shot but i find it hard to believe that some wall junk on a half inch hole would affect things that much. But then again stranger things have happened. I'll take off the TB and give that whole thing a good cleaning i guess.

Motor and tranny mounts... Its a thought but seems a bit much. I cant believe that at 64k they would be gone or that a car company would release a car that the transmission/engine acted as its doing right now on a stock setup. but non-the-less if my sensor fooling around doesnt work out i will keep an open mind.

Thanks for the responses... the more the merrier!


On another note... one thing i thought was that perhaps the TPS is a hair off and when the TB is becoming completely closed a second before it is able to register absolute zero to the ECU so the IAC is a smidge off. Frankly the adjustment for the TPS is quite a shoddy setup. Two screws and move the whole unit to adjust... pft... should be an adjustable potentiometer or something that allows you a more exact adjustment instead of moving a whole module in a semi tight space.

Last edited by DenT; 02-08-2009 at 10:50 AM.
DenT is offline   Reply With Quote
Old 02-08-2009, 11:57 AM   #6
RaceFaceXC
NASIOC Supporter
 
Member#: 165749
Join Date: Dec 2007
Chapter/Region: South East
Location: stupid Florida
Vehicle:
2007 No YELLING
on the bus!

Default

Quote:
Originally Posted by nojokesniper View Post
ur iac is causing it, when you let off the gas pedal, the throttle body closes, then the iac is supposed to open to let air bypass the throttle body so the car does not stall, but if your iac is not moving as well or as fast as it could your car is essentially almost stalling right when you let off the gas but then your iac slowly opens and allows it to run like it should

i would try to clean the IACs passage, maybe you have crud in there, if not maybe its time for a new iac
I disagree. Here's why:

This doesnt only happen when slowing to idle or accel from idle... it happens anytime you are on/off the gas in 1/2nd gear (even 3rd a bit). Im pretty sure the IACV doent do its job until the RPM's are near idle, weather the throttle plate is open or closed.

As far as the mounts being the fix for this, i cant say I know for sure (i havnt done it myself, yet) but I have read on several threads that it flat out eliminated the jerkyness of 1/2 gear for the people who did it. It is a $200 mod + time/labor to install the mounts if you pay retail. An increase in NVH is sure to happen, too. And it makes sense that it would at the least make it much better.
RaceFaceXC is offline   Reply With Quote
Old 02-08-2009, 02:26 PM   #7
DenT
Scooby Newbie
 
Member#: 201779
Join Date: Feb 2009
Location: Tri State
Vehicle:
2003 Impreza TS

Default

Quote:
Originally Posted by RaceFaceXC View Post
I disagree. Here's why:

This doesn't only happen when slowing to idle or accel from idle... it happens anytime you are on/off the gas in 1/2nd gear (even 3rd a bit). Im pretty sure the IACV doent do its job until the RPM's are near idle, weather the throttle plate is open or closed.
well granted i haven't done my usual full fledged research yet... but i will still keep it as a possibility to look into. Besides that is the code that my engine is throwing P0519...

I still find it EXTREMELY hard to believe that upgraded mounts are required to not have the car bounce just by taking your foot off the throttle. I doubt it did it off the lot. perhaps i'll track down someone with a similar model and take it for a spin. but again i will keep that as my last thing to look it...
DenT is offline   Reply With Quote
Old 02-08-2009, 03:32 PM   #8
chazly413
Scooby Specialist
 
Member#: 151079
Join Date: Jun 2007
Chapter/Region: MAIC
Location: College Park, MD
Vehicle:
2005 2.5RS RBP
motec system exhaust-RIP

Default

This is what subarus do. It's just a fact lol My dads 96 legacy did it off the lot, mine did it when I got it at 16k miles.
chazly413 is offline   Reply With Quote
Old 02-08-2009, 04:05 PM   #9
RaceFaceXC
NASIOC Supporter
 
Member#: 165749
Join Date: Dec 2007
Chapter/Region: South East
Location: stupid Florida
Vehicle:
2007 No YELLING
on the bus!

Default

Quote:
Originally Posted by DenT View Post
well granted i haven't done my usual full fledged research yet... but i will still keep it as a possibility to look into. Besides that is the code that my engine is throwing P0519...

I still find it EXTREMELY hard to believe that upgraded mounts are required to not have the car bounce just by taking your foot off the throttle. I doubt it did it off the lot. perhaps i'll track down someone with a similar model and take it for a spin. but again i will keep that as my last thing to look it...
Mine did it off the lot. keep us posted of what happens when you remedy the P0519, im curious if it will make it better, eliminate it all together, or not make any difference.
RaceFaceXC is offline   Reply With Quote
Old 02-08-2009, 10:27 PM   #10
sa4baru
Scooby Newbie
 
Member#: 195354
Join Date: Nov 2008
Location: State College, PA
Default

timing advance reduces this alot. an open source tune could help you out.
sa4baru is offline   Reply With Quote
Old 02-08-2009, 10:41 PM   #11
sniper1rfa
Scooby Specialist
 
Member#: 141040
Join Date: Feb 2007
Chapter/Region: NESIC
Location: Designing things
Vehicle:
07 2.5i wagon
UGM

Default

Quote:
Originally Posted by DenT View Post
I doubt it did it off the lot. perhaps i'll track down someone with a similar model and take it for a spin.

Mines done it since mile 7. It's particularly bad at low speeds in 3rd. Diff bushings helped a lot, and i'm sure engine and tranny mounts would also. The DBW system doesn't help any.

My brother's 02 was not as bad, but still a bit touchy sometimes, particularly at low speeds. I think that was entirely due to soft mounts and driveline slack.
sniper1rfa is offline   Reply With Quote
Old 02-08-2009, 11:27 PM   #12
DenT
Scooby Newbie
 
Member#: 201779
Join Date: Feb 2009
Location: Tri State
Vehicle:
2003 Impreza TS

Default

Quote:
Originally Posted by sa4baru View Post
timing advance reduces this alot. an open source tune could help you out.
haha this blows my mind that i have to consider this stuff for a bone stock impreza... what did i get myself into...
DenT is offline   Reply With Quote
Old 02-08-2009, 11:49 PM   #13
RaceFaceXC
NASIOC Supporter
 
Member#: 165749
Join Date: Dec 2007
Chapter/Region: South East
Location: stupid Florida
Vehicle:
2007 No YELLING
on the bus!

Default

Quote:
Originally Posted by DenT View Post
haha this blows my mind that i have to consider this stuff for a bone stock impreza... what did i get myself into...

a bone stock impreza is an econobox.
RaceFaceXC is offline   Reply With Quote
Old 02-09-2009, 05:08 AM   #14
Counterfit
Scooby Guru
 
Member#: 124254
Join Date: Aug 2006
Chapter/Region: NESIC
Location: Rhode Island
Vehicle:
2006 06 SGM Slowbaru
"The Scoobinator"

Default

20mpg is not econobox range.
Counterfit is offline   Reply With Quote
Old 02-09-2009, 07:27 AM   #15
RaceFaceXC
NASIOC Supporter
 
Member#: 165749
Join Date: Dec 2007
Chapter/Region: South East
Location: stupid Florida
Vehicle:
2007 No YELLING
on the bus!

Default

$18,000 out the door and 29 highway 26 city is econobox.
RaceFaceXC is offline   Reply With Quote
Old 02-09-2009, 11:40 AM   #16
pacotaco
Scooby Newbie
 
Member#: 202170
Join Date: Feb 2009
Chapter/Region: MAIC
Location: NOVA
Vehicle:
2004 saab 9-3
black

Default

mine does it and i know i have an injector problem so you might have bad injectors i get the cut but i mean my injectors cut out when your pushing it so it might be your injectors. cuz when you let off the gas it cuts fuel slowly i think and if their bad then it could cause that
pacotaco is offline   Reply With Quote
Old 02-09-2009, 01:48 PM   #17
DenT
Scooby Newbie
 
Member#: 201779
Join Date: Feb 2009
Location: Tri State
Vehicle:
2003 Impreza TS

Default

Well I ordered a TB gasket and when it comes in i'll rip that sucker apart and clean it (brings back memories of the annual motorcycle carb cleaning) to try to get rid of the P0519 code comming up.

After riding a bit more i opened my mind that the mounts may be on their way out. I'll jack it up and inspect. I figure they could be on the way out sooner than a 2wd car as there's not much forgiveness for clutch dropping via spinning tires leading to faster wear. + the previous driver did mostly local miles which would be a lot of tranny action (get your mind out of the gutter).

I'll keep you posted!
DenT is offline   Reply With Quote
Old 02-09-2009, 02:03 PM   #18
Counterfit
Scooby Guru
 
Member#: 124254
Join Date: Aug 2006
Chapter/Region: NESIC
Location: Rhode Island
Vehicle:
2006 06 SGM Slowbaru
"The Scoobinator"

Default

Quote:
Originally Posted by RaceFaceXC View Post
$18,000 out the door and 29 highway 26 city is econobox.
****, I wish I was getting 26mpg. Stupid heavy-ass steel wheels/winter gas/heavy right foot.
Counterfit is offline   Reply With Quote
Old 02-09-2009, 07:12 PM   #19
DenT
Scooby Newbie
 
Member#: 201779
Join Date: Feb 2009
Location: Tri State
Vehicle:
2003 Impreza TS

Default

Well i Got the car up on jack stands when i got home and all the mounts look good to go. Jamming a pry bar in there the stock mounts do allow a decent amount of horizontal movement of the tranny, but the mount itself looks to be in good (OEM) shape. I will say that the pictures of the group N are quite a bit stiffer looking than the stockers...I'm not ready to cross that bridge yet though..

http://www.subaruwrxparts.com/produc...unt-p-314.html

http://autoparts.cardomain.com/auto-...smission-mount


TB gasket and such should be in tomorrow...
DenT is offline   Reply With Quote
Old 02-09-2009, 08:33 PM   #20
RaceFaceXC
NASIOC Supporter
 
Member#: 165749
Join Date: Dec 2007
Chapter/Region: South East
Location: stupid Florida
Vehicle:
2007 No YELLING
on the bus!

Default

Quote:
Originally Posted by DenT View Post
Well i Got the car up on jack stands when i got home and all the mounts look good to go. Jamming a pry bar in there the stock mounts do allow a decent amount of horizontal movement of the tranny, but the mount itself looks to be in good (OEM) shape. I will say that the pictures of the group N are quite a bit stiffer looking than the stockers...I'm not ready to cross that bridge yet though..

http://www.subaruwrxparts.com/produc...unt-p-314.html

http://autoparts.cardomain.com/auto-...smission-mount


TB gasket and such should be in tomorrow...
It's not that the mounts are worn/damaged its that they are just too soft.
RaceFaceXC is offline   Reply With Quote
Old 02-10-2009, 12:29 AM   #21
yarrgh
Scooby Specialist
 
Member#: 80465
Join Date: Jan 2005
Chapter/Region: RMIC
Location: Aurora, CO
Vehicle:
2001 2.5RS
Black Diamond Pearl

Default

Quote:
Originally Posted by DenT View Post
Well I ordered a TB gasket and when it comes in i'll rip that sucker apart and clean it (brings back memories of the annual motorcycle carb cleaning) to try to get rid of the P0519 code comming up.

After riding a bit more i opened my mind that the mounts may be on their way out. I'll jack it up and inspect. I figure they could be on the way out sooner than a 2wd car as there's not much forgiveness for clutch dropping via spinning tires leading to faster wear. + the previous driver did mostly local miles which would be a lot of tranny action (get your mind out of the gutter).

I'll keep you posted!
depending on how much you rip apart, note the exact orientation of the TPS. If you don't remove it, disregard this. If you do, mark it w/some paint or cut a notch in the TB/TPS. It needs to go on at a certain position and have a certain voltage at 0% throttle.
yarrgh is online now   Reply With Quote
Old 02-10-2009, 02:21 AM   #22
Blase
Scooby Newbie
 
Member#: 54702
Join Date: Feb 2004
Chapter/Region: MWSOC
Location: Chicago area
Vehicle:
2000 impreza 2.5rs
brp

Default

If the codes is for high idle one thing to check, as far as the cel for the iac goes, is the tension on the throttle cables themselves. For the longest time I swore that my IAC crapped out. I cleaned and cleaned until I could almost see my reflection, and i still had problems. I didn't think to check if the throttle cables were just too tight, and of course they were.

Also, the hesitation you're having is probably not related. My car has done that since I got it. Just learn to press the clutch in when cruising around in low gears and deaccelerating.
Blase is offline   Reply With Quote
Old 02-10-2009, 08:22 AM   #23
DenT
Scooby Newbie
 
Member#: 201779
Join Date: Feb 2009
Location: Tri State
Vehicle:
2003 Impreza TS

Default

yarrgh:

Yeah i already learned that one... took it off to see what it was and figured it out really quick... i didnt do the whole multimeter at the ECU... rather i kind of cheated and put my OBDII reader in Live data mode and adjusted the TPS based on the Absolute Throttle % readout...

Blase:
Tension is good to go. check it last night as i thought it might be too loose. in actuality there is about an 1/8th inch of play in each of the cams before it engages the buterfly (supposed to be) so they are alright.
As for slipping the clutch when decelerating. perhaps it will come to that but it just seems a bit silly... I can rev my bike to 12-13k... blip off the throttle and transition to a smooth deceleration even with a chain. Perhaps i will consider some stiffer or new mounts in the future.

Actually i was thinking... i could test out the mount theory by temporarily bolting on a clamping device (some homebrew stuff) that would lock/stiffen the current mount in place for a quick spin around town. Perhaps i'll give that a shot next week.
DenT is offline   Reply With Quote
Old 02-10-2009, 11:52 AM   #24
Blase
Scooby Newbie
 
Member#: 54702
Join Date: Feb 2004
Chapter/Region: MWSOC
Location: Chicago area
Vehicle:
2000 impreza 2.5rs
brp

Default

Your honda and bike have different power bands and gearing than your subaru, not to mention the awd. Its like comparing apples to oranges.
Blase is offline   Reply With Quote
Old 02-10-2009, 12:25 PM   #25
DenT
Scooby Newbie
 
Member#: 201779
Join Date: Feb 2009
Location: Tri State
Vehicle:
2003 Impreza TS

Default

i understand... i wasn't trying to side by side compare them...

I was just using an example of engineering feats...

besides this slop is not power band specific...
DenT 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
FS : FL 04-07 Sti Blitz throttle controller Imprezsti5 Engine/Power/Exhaust 5 06-03-2010 05:27 PM
Rattle after throttle release oburgslim Factory 2.0L Turbo Powertrain 2 05-17-2007 07:41 AM
Throttle not releasing in 1st gear after WOT, AP STG2 93oct 06 WRX ShagnRS AccessPort 50 11-25-2006 05:50 PM
Possible to disable upshifts in 4eat when throttle is released? StuBeck Transmission (AT/MT) & Driveline 5 07-09-2003 02:20 AM
CobbTuning Throttle Body released... SCOOBYSHAG General Forum Archive 9 08-29-2000 05:09 PM


All times are GMT -4. The time now is 08:52 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.